Page:Insects - Their Ways and Means of Living.djvu/135

 AND MEANS OF LIVING

one bud became contiguous with the one before, or became enveloped by it, a relation would be established between the two buds similar to that which exists between succes- sive generations of lire forms. The so-called parent gen-

eration, in other words, contains the germs of the succeeding generation, but it does not produce them. Each generation is simply the custodian of the germ cells entrust- ed to i t, and the "off- spring" resembles the parent, not because it is a chip off the parental block, but because both parent and offspring are developed from the same line of germ cells. Parents create the conditions under wli, ch the germ cells will de- velop; they nourish and protect them during the period of their develop- ment; and, when each generation has served the purpose of its ex- istence, it sooner or later dies. But the in- dividuals produced from

F,c. 64. The leg of a young grasshopper, showing the typical segmentation of an insect's leg The leg is supported on a pleural plate (Pi) in the lateral wall of its segment. The basal segment of the free part of the leg is the coxa (Cx), then comes a small trochanter (Tf), next a long femur (F) separated by the knee bend from the tibia (Tb), and lastly the foot, consisting of a sub-segmented tarsus (Tar), and a pair of terminal claws (CI) with an ad- hesive lobe hetween them

its germ cells do the same

for another set of germ cells produced simultaneously with themselves, and so on as long as the species persists. To express the facts of succession in each specific form of animal, then, we should analyze each generation into germ cells and an accompanying mass of protective cells which

[i]

INSECTS