Page:Science vol. 5.djvu/421

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��oil the effetta of llie apijUealion of stiuiiilants — mechanical, electrical, and chemical — are described. The action of poisons upon jelly- fishes shows a mouderfnl resemblaoce to that of the same on higher animals. Many con- clusive experiments are given to prove that the fatal effects of transferring medusae from salt to fresh water is not due to a difference in density of the two media. A medusa arti- ficially frozen into a solid block of ice. so that ice-crj-atals are formed in its body, is not kille<l by the operation.

The observations on the star-fishes and sea- urchins are recorded in n single chapter; yet they are in many respects as interesting as those on the jelly-flshes in the preceding nine chaptei-s. The author points out the different methods adopted by star-fishes and sea-urchins in righting themselves when turned upon their backs. The ' geometrical regularity ' of these animals, in their nervous system as in their form, leads to a " very pretty instance in physiology of the physical principle of the parallelogram of forces." If two stimuli are applied simultaneously at opposite extremities of an axis passing horizontally through a round sea-urchin, the Echinus moves off ' in a direc- tion at right angles ' to a line connecting these (Kiints.

Tlic author finds, that, by ciittiug off the eye-spots from several slar-Gshes and sea- urchins, they do not seek the light thrown into the dish, as is invariably their habit when these organs are intact. He also finds that an ex- cised raj- of a star-fleh makes its way to the beam of light as ir it were an entire animal. A star-fish, with all the eye-spots but one re- moved, crawls to the light.

Romanes ascribes to the star-fish a sense of smell from the following experiments : a star- fish is kept fasting for seieral days. A piece of shell-fish is then placed in the tank with the animal. He immediately crawled toward it. •-Jloreover," says the author, " ifa small piece of the food were" held in a pair of forceps, and gently withdrawn as the star-fish approached it, the animal could be led about the fioor of the tank in any direction, just as a hungry dog could be led about by continually withdrawing from his nose a piece of meat as lie continu- ally follows it up." To determine the region of the body where the supposed sense of smell is located, the experimenter removed the eye- spots, and the hungry star-fish moved iu the direction of its food. He varnished the whole upper (aboral) surface of the body, and still the aculeuesB of the sense was not diminished. He concludes that the sense is not localized.

��except that it is ■■distributed over the whole of the ventral or lower surface of the animal."

These last- mentioned experiments can be easily tested by any one without elaborate ap- paratus. Certiiinly one great value of all the experiments is their great simphcity ; and the book has this strong recommendation to con- tribute to make it. what the author expresses a wish that it should be, a " book of service to the working physiologist."

The work of Romanes is certainly one of the most valuable contributions to the physiology of the primitive nervous system which have heen publisbetl, and it is the only book on this sub- ject which has yet appeared in America. Yet, much as there is to praise in this book, there are several statements which an anatomist can- not accept ; but these do not detract from the excellence of the work, as far as the main questions are concerned.

��MINOR BOOK NOTICES.

Pkofessok Joiissos's little book on curve- tracing is more clearly arranged than Frost's treatise, and seems much better suited to the wants of readers who need only a general knowledge of methods, and do not wish to go into refinements of approximation which they may seldom or never have occasion to use. Students rarely think it worth while to spend much time in curve-tracing afler they have onee acquired a little knowledge of analytic geome- try ; but every mm who means to devote his attention specially to mathematics needs to have some facility in interpreting equations geo- metrically, and this he can best get by studying some such book as the present one. Professor Johnson treats the analytical triangle in a way which will recommend itself, we feel sure, to mathematicians, aud introduces it so early that .1 person who has time for no more can read the first half of the book to advantage. In a few instances the addition of a short clause would moke clear sentences which are now rather obscure.

Pettil's little book gives in a concise form a brief account of nearly all the more important

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