2l6 



THE EVOLUTION OF 6 EX. 



reproduction in multicellular organisms, whether they multiply by 

 asexual budding or by differentiated sex-elements. But in the preced- 

 ing chapter, following Spencer, we have emphasized the connection 

 between division and a katabolic predominance within the cell. A 



' Fig. 83. — Division of an Animal Celi, showing the nucleus (a) in process of 

 forming two daughter-nuclei, showing also the protoplasmic 

 network (/>). — From Carnoy. 



constructive period may precede, but a disruptive climax attends the 

 division. So far then as reproduction is either wholly included in the 

 process of cell-division, or has this as its necessary precedent, it is 

 associated with a katabolic crisis. 



IV. Argument from the Gradations between Asexual Sev- 

 erance of Parts and the Liberation of Special Sex-cells. — 

 Discussing asexual reproduction, we have noticed that some worm- 

 types break into two or more parts, which start new individuals. That 

 some nemerteans normally break up into pieces, as they do in the 

 feverish anxiety of capture, is most probable; and this is certainly the 

 case in certain annelids. From a syllid, which sets free a sexual 

 individual, the overgrowth of an asexual parent to one which liberates 

 a series of joints, or even a single joint, bearing reproductive elements, 

 is but a slight step. From the last case to the rupture which liberates 

 sex-elements is again only a slight advance. A similar series is well 



