THE POSITION OF SPONGES, ETC. 427 



I.— THE SPONGES AS PROTOZOA. 



The older observers, whose histological technique con- 

 sisted for the most part of tearing up bits of living sponges 

 with needles, and examining preparations made in this 

 way with microscopes which we should not now consider 

 very tirst rate, nearly all considered sponges as Protozoa. 

 In their preparations they always saw amoeboid cells, which 

 could be observed to move about, and sometimes they saw 

 flagellated cells as well. Hence sponges were regarded as 

 colonial forms of Rhizopods, or as masses of Infusorians, 

 intermediate between amoebae and monads. The former 

 view, advocated by Perty (1852, p. 185), was advanced by 

 Carter (1848, p. 310), who says of the fresh- water sponges : 

 *' The animals of which they are but a congeries are iden- 

 tical with the infusorium Proteus ". The second view, put 

 forward by Dujardin {1841, p. 306), is the opinion to- 

 wards which LieberkLihn (1856, p. 512) was more inclined. 

 Saville Kent (1870, p. 217) also regarded the sponge body 

 as " an agregation of amoebiform animals, building up 

 amongst themselves a common skeletal support," and con- 

 siders sponges, "in a natural and morphological system of 

 classification, to be ranked as the highest representatives of 

 the Protozoa ". 



The theory of the Protozoan nature of sponges took an 

 entirely new turn with the discovery by James-Clark {1867) 

 of the collar cells of sponges and their great similarity, 

 amounting almost to identity, with the peculiar class of 

 flagellate Infusorians, named by Saville Kent Choano- 

 flagellata. James-Clark (p. 324) declared the sponges to 

 be simply colonies of Choanoflagellata, and expressed the 

 opinion that the collar cells of the difl^erent genera of 

 sponges would be found to resemble the various genera 

 of the collared monads, so that it would be possible to 

 divide the genera of sponges amongst the families of the 

 Choanoflagellata. 



Both Carter and Saville Kent were converted to this 

 view, and it may be said that the appearance of James- 

 Clark's memoirs was practically the end of all discussion 



29 



