428 SCIENCE PROGRESS. 



as to the Rhizopod affinities of sponges. Carter, however, 

 combined an acquiescence in James-Clark's theory of the 

 Choanoflagellate affinities of sponges with pecuHar views 

 of his own as to the relationship of sponges to compound 

 Ascidians. He invented the term " spongozoon " or sponge 

 animal for the collar cell, and in 1872 he says (p. 47): 

 " The spongozoon ... is ^/le animal which constructs the 

 sponges generally". In 1874, discussing the flagel- 

 lated chambers, or ampullaceous sacs as he termed them, 

 he places under this head-line the query (p. 436), " Haec- 

 kel's 'gastrula' when developed in situ ?" He goes on to 

 remark (p. 438) : " At one stage the young Ascidian is 

 almost identical in appearance with the ampullaceous sac, 

 that is, composed of a pavement of cells aggregated into a 

 sac-like form. . . , The development of the ampullaceous 

 sac is arrested, and the cells adapt themselves to that con- 

 dition which ends in the evolution of a sponge ; while the 

 sac and its cells in the development of an Ascidian grow to 

 the evolution of a compound tunicated group." After a 

 comparison of the human ovum and a Protozoon he says : 

 " Hence we see that an organic cell may be at one time 

 one thing, and at another another, arising simply from 

 adaptation to the functions required. Thus the cell or 

 spongozoon of the ampullaceous sac becomes an individu- 

 alised animal, and the luhole sac, with its oral and anal 

 apertures, so far like an Ascidian ; while the sac with its 

 pavement-lining of cells in the compound tunicated animal, 

 goes on unarrested to produce an Ascidian." And he adds : 

 " To produce the ' adaptation ' there must be, of course, a 

 creative or directing power, which being iiijinite, we can 

 never comprehend ". 



Kent in his Manual of the Infusoria (1881, vol. i.) 

 devoted a chapter to the affinities of sponges and 

 argues strongly for classifying them with the Flagellata 

 amongst the Protozoa. Besides the great resemblance of 

 the collar cells to the Choanotiagellata he brings forward 

 other grounds in support of his argument, some of which 

 have not been confirmed, while others have been found 

 erroneous by subsequent observers. His most valuable 



