Page:Encyclopædia Britannica, Ninth Edition, v. 19.djvu/884

Rh 860 PEOTOZOA [RIIYNCHOFLAGELLATA. possess a girdle of cilia as previously supposed, but that the struc ture mistaken for cilia is a second flagellum which lies horizontally in the transverse groove. Hence the name Ciliotlagellata is super seded by Dinoflagellata (Gr. dinos, the round area where oxen tread out on a threshing floor). i J. XXII. Dinoflagellata and Bhynchonagellata. x.n. In all these figures the apparent girdle of cilia is, according to Klebs and hiitsclili s recent discovery, to be interpreted as an encircling flagellum lying in the transverse groove. 1. Peridinium uberriminn, Allman ; x 300 (fresh water ponds, Dublin). Probably (according to ISiitschli) the processes on the surface are not cilia nor flagellum. Both the longitudinal and the transverse groove are well seen. 2. The same species in transverse Ission. 3. Dinophystf ovata, 01. and L; x3f&amp;gt;0(salt water, Norwegian 4. Dinophytit acuminata, Cl. and L. ; x350 (salt water, Norwegian coast). 5. Qymnodinium, sp. ; xfiOO. 6. Prorocen- Ehr.; 100 &amp;lt; all iratei 7. Dorsal aspect of the Mine gpi&amp;gt;-. 8, 9. Cysts of Peridinia; the contents of 8 divided into eight minute naked Peridinia; x.SOO. 10. Empty cuirass of CeraUum dimnjem. Cl. and L. ; x500 ; showing the form and disposition at its component plates. 11. The same species with the animal con tracted into a spherical form. The transverse groove well seen. 12. The same species in the normal state. The apparent girdle of cilia is really an undulating flagellum lying in the transverse groove. 13, 14. Young stages of Koetifuea miliarin. n, nucleus:, the so-called spine (superficial ridge of the adult); a, the big flagellum ; the unlettered filament is a flagellum which becomes the oral flagellum of the adult. 15. Cera- tittiii tripos, Mull. The transverse groove well seen. The cilia really are a single horizontal flagellum. 10, 17. Two stages in the transverse fission of Soctiliica niiliarin, Suriray. n, nucleus; N, food-particles; t, the muscular flagellum. 18. Nuctiluca miliaris, viewed from the aboral side (after Allman, Quart. Jour. Mic. Sci., 1872). a, the entrance to the atrium or flagellar fossa (longitudinal groove of Dinoflagellata) ; c, the superficial ridge; d, the big flagellum ( = the flagellum of the transverse groove of Dinoflagellata); h, the nucleus. 19. The animal acted upon by iodine solution, showing the protoplasm like the &quot; primordial utricle&quot; of a vegetable cell shrunk away from the structureless firm shell or cuirass. 20. Lateral view of Noctiluca, showing a, the entrance to the groove-like atrium or flagellar fossa in which b is placed ; c, the superficial ridge; d, the big flagellum; e, the mouth and gullet, in which is seen Krohn s oral flagellum (=the chief flagellum or flagellum of the longitu dinal groove of Dino-flagellata) ; /, broad process of protoplasm extending from the superficial ridge c to the central protoplasm ; g, duplicature of the shell in connexion with the superficial ridge ; h, nucleus. Biitschli further suggests that the Dinoflagellata with their two flagella and their 1-shaped combination of longitudinal and transverse grooves niay be derived from the Cryptomonadina (see p. 858). In the latter a groove-like recess is present in connexion with the origin of the two fiagella. Biitschli thinks the large pro boscis-like flagellum of Noctiluca (Rhynchoflagcllata) represents the horizontal flagellum of Dinoflagellata, whilst the prominent longitudinal ilagelhim of the Dinoflagellata is represented in that animal by the small flagellum discovered by Krohn within the gullet (see Fig. XXII. 20, e). The young form of Noctiluca (Fig. XXII. 14) has the longitudinal flagellum still of large size. The phosphorescence of many Dinoflagellata is a further point of resemblance between them and Noctiluca. Bergh has shown that there is a considerable range of form in various species of Dinoflagellata (Ceratium, &c.), and has also drawn attention to the curious fact that the mode of nutrition (whether holophytic or holozoic) dilFers in allied species. Possibly it may be found to differ according to the conditions of life in individuals of one and the same species. The drawings in Fig. XXII. were engraved before the publication of Biitschli s confirmation of Klebs s discovery as to the non-existence of cilia in the transverse groove. The hair-like processes figured by Allman (91) external to the transverse groove in his Fcridinium ubcrrimum (Fig. XXII. 1, 2) cannot, however, be explained as a flagellum. Biitschli inclines to the opinion that their nature was misinterpreted by Allman, although the latter especially calls attention to them as cilia, and as rendering his P. iibcrrimum unlike the Peridinium of Ehrenberg, in which the cilia (horizontal flagellum) are confined to the transverse groove. CLASS IV. EHYNCHOFLAGELLATA, Lankester. Characters. Corticate Protozoa of large size (-^th inch) and globular or lenticular form, with a firm cuticular membrane and highly vacuolated (reticular) protoplasm. In Noctiluca a deep groove is formed on one side of the spherical body, from the bottom of which springs the thick transversely striated proboscis or &quot;big flagellum.&quot; Near this is the oral aperture and a cylin drical pharynx in which is placed the second or smaller flagellum (corresponding to the longitudinal flagellum of Dinoflagellata). Nutrition is holozoic. No contractile vacuole is present ; granule- streaming is observed in the protoplasm. An alimentary tract and anus have been erroneously described. The nucleus is spherical and not proportionately large (see for details Fig. XXII. 18 to 20). Reproduction by transverse fission occurs, also conjugation and, either subsequently to that process or independently of it, a forma tion of spores (Cicnkowski, 87), the protoplasm gathering itself, within the shell-like cuticular membrane, into a cake which divides rapidly into numerous flagellated spores (flagellulffi). These escape and gradually develop into the adult form (Fig. XXII. 13, 14). The proboscis-like large flagellum is transversely striated, and exhibits energetic but not very rapid lashing movements. Noctiluca is phosphorescent, the seat of phosphorescence being, as determined by Allman (86), the cortical layer of protoplasm underlying the cuticular shell or cell-wall as the primordial cuticle of a vacuolated vegetable cell underlies the vegetable cell-wall. Genera. Only two genera (both marine) are known : Nodiluca, Suriray (90) (Fig. XXII. 17-20) ; Lcptodiscus, Hertwig (88). Further Remarks on the FJiynchoflafjcllata. The peculiar and characteristic feature of Noctiluca appears to be found in its large transversely-striated flagellum, which, according to Biitschli, is not the same as the longitudinal flagellum of the Dinoflagellata, but probably represents the horizontal flagellum of those orgMiiisms in a modified condition; hence the name here pioposed Rhyncho- flagellata. Noctiluca is further remarkable for its large size and cyst-like form, and the reticular arrangement of its protoplasm, like that of a vegetable cell. This is paralleled in Trachclius ovum among the Ciliata (Fig. XXIV. 14), where the same stiffening of the cuticle allows the vacuolation of the subjacent protoplasm to take place. The remarkable Lcptodiscus mcdusoidcs of R. Hertwig (88) appears to be closely related to Noctiluca. It would no doubt be not unreasonable to associate the Dino-