604 APPENDIX D2. 



And then on the preceding page, referring to the composition of 

 the Annelid body, he says : " The most natural comparisons are 

 those with the tapeworm chain and with the strobila of the 

 Scyphomedusse." Now since it is here assumed that the tape- 

 worm and the strobila are analogous in composition, it is implied 

 that the detached proglottis and the detached medusa are analo- 

 gous ; and hence if we are to regard the proglottis as " not a com- 

 plete individual but only the abstricted hinder portion of the body 

 of the Cestode," then we must similarly regard the medusa as not 

 a complete individual, but only the abstricted hinder portion of 

 the strobila. This commits us to the strange conclusion that 

 whereas individuality is ascribed to the original simple polyp, 

 and by-and-by to the partially-segmented strobila, though these 

 are without special senses and with only rudiments of muscular 

 and nervous systems, individuality is denied to the detached 

 medusa, which has organs of sense, a distinct nervo-muscular 

 system and a considerable power of locomotion, as well as a 

 generative system : traits which in other cases characterize 

 developed individuals. Here also, then, there seems to be an 

 inversion of the ordinary conception. 



This conception of the proglottis and the medusa is, I see, 

 accepted by some as tenable. But if we accept it we must accept 

 also an analogous conception, which will I think be regarded as 

 untenable. It is that supplied by the Aphides. From an egg 

 proceeds a series of sexless and wingless females, and at the end 

 of the series there come winged males and females with resulting 

 gamic reproduction. If instead of forming a discrete series the 

 imperfect females formed a concrete series, the members of which 

 could individually feed without being detached from one another, 

 as the segments of a tapeworm can, the parallelism would be 

 complete ; and then, according to the view in question, we should 

 have to regard the perfect males and females eventually arising, 

 not as individuals but as terminal portions of the series, contain- 

 ing generative products and having wings for the dispersion of 

 them locomotive egg-bearing segments of the chain. Whoever 

 espouses this view must hold either that the first imperfect female 

 of the series was the individual or that the entire string of them 

 constituted the individual (in conformity with a view once pro- 

 pounded by Prof. Huxley). But he must do more than this. 

 Since the Aphides have descended from some winged species of 

 the order Ifemiptera, he must hold that among those remote 

 ancestors each particular fly, male or female, was an individual ; 

 but that when abundant food and inert life led to the partheno- 

 genetic habit, and to chains of sexless forms, the males and 

 females eventually produced at the end of each chain, though, 

 like their remote ancestors, possessed of procreative organs and 

 wings, are not individuals. 



