310 Dynamic Theory. 



reproducing the next generation, but that is the rule in some species of 

 the annelid Polygordius, in which "the mature females break up and 

 die in liberating their ova. This is approached but suggestively 

 avoided in a genus of capitellid sea-worms ( Clitomastus). The whole 

 organism is not sacrificed, but only an abdominal portion of the body. 

 This is, in fact, one of the key-notes to reproductive differentiation 

 the sacrifice is lessened and the fatality warded off. " ( G. & T.) 



But, again, we find in some thread-worms, or nematodes, ( e. g. , As- 

 caris dactyluris ) that the young live at the expense of the mother until 

 she is reduced to a mere husk. Similar sacrifice is noted in the case 

 of many other of these simple organisms. There are many insects lo- 

 custs, butterflies, ephemerids, &c. , which die a few hours after the pro- 

 duction of the ova, the exhaustion of the reproduction being fatal to 

 both female and male. In all such cases the differentiation of the re- 

 productive cells from those of the rest of the body, or rather the differ- 

 entiation of the rest of the body from them, has not proceeded so far 



FIG. 130. Diagram showing the relation between Reproductive 

 Cells and the Body. The continuous chain of dotted cells, at the 

 bottom, represents a succession of Protozoa; further on it repre- 

 sents the ova, from which the bodies, in more advanced life, are 

 produced ; the undotted cells and the projections to the right being 

 the bodies- At each generation a spermatozoon fertilizes the liber- 

 ated ovum. ( After Geddes & Thomson.) 



that the body can live without them. The nearer the 

 organism is to the protozoa the less important the body 

 outside of the reproductive department is. See fig. 130. 

 In the single-celled protozoa it is nil, for the single 

 cell is body and reproductive organs all in one, or 

 rather the reproductive cell is all there is of it, and 

 there is no body. Its disruption upon maturity ends 

 with two live cells in place of the previous one, and no 

 dead body, on which account it is said the protozoa 

 are immortal. It may be said with equal truth that 

 the reproductive portion of all organisms is immortal. 

 This is illustrated by fig. 130, which shows the con- 

 tinuous life of the line of reproductive cells, and from 

 this, as a single stem is set off at each generation, the 

 general mass of the body, which, after surviving its 

 term of life, suffers dissolution. It is true that the 

 bod} r exercises a reciprocal formative influence upon 

 the cells of reproduction, and to that extent shares in 

 their immortalit3 r , but the substance of the latter with- 

 \ out loss is incorporated- in the new generation. 



FIG 130. ^ appears that between the multiple union of the 



amoeboid individuals, which results in the formation of a "plasmo- 

 dium," as in Protomyxa, and the dual union or sexual union of two 



