366 M. F. E. Schulze on the Relationship 



between the collared cells of the Sponges and those flagellate 

 Infusoria, occurring sometimes singly and sometimes in 

 colonies, which are denominated Choanoflagellata by Saville 

 Kent and by Btitschli Calicomastiges. This resemblance 

 is the more striking because we do not meet with similar 

 structures elsewhere in the whole animal kingdom. In 

 both cases we have to do with a cylindrical or rounded 

 plasma-body with contained granules and a well-developed 

 nucleus. From the middle of the somewhat prominent free 

 end-surface originates a flagellum, and from the outer circular 

 margin freely projects the so-called collar, an extremely deli- 

 cate hyaline annular membrane, which generally exhibits the 

 form of a cylindrical mantle, but is also susceptible of certain 

 changes of form. Thus we may observe sometimes an 

 abbreviation, sometimes a funnel-like enlargement or a con- 

 traction of the tube outwardly, sometimes a bellied inflation. 

 Those small limpid vacuoles which regularly occur in the 

 Choanoflagellata in the basal part, and perform rhythmical 

 pulsations, are also asserted by some naturalists, such as 

 James Clark, Carter, and Saville Kent, to be constant and 

 characteristic structures of the collared cells of Sponges ; but I 

 have by no means found them regularly in the hitter. Granu- 

 lar pigment-masses, such as occur, often abundantly, in the 

 collared cells of SpongeUa, Oscarella, and other Sponges, have 

 hitherto not been observed in the Choanoflagellata. 



Although these and other differences may appear insigni- 

 ficant in comparison with the remarkable agreement which is 

 expressed in the peculiar collar, it is nevertheless clear that 

 even so close a resemblance between certain unicellular Pro- 

 tozoa and individual cells of the Sponges (which consist of 

 three different tissue-layers) can by no means alone lead to 

 the conclusion that the Sponges belong to the Protozoa. The 

 untenability of such a conclusion becomes still plainer (as, 

 indeed, Lendenfeld * has lately pointed out) if we apply 

 it to other groups of animals, and refer the Cnidaria, for 

 example, to the Protozoa, because their gastro-vascular 

 system is lined with flagellate cells, which resemble certain 

 Flagellata. 



Saville Kent j" himself seems to have felt the insufficiency 

 of such a proceeding, 'as he has endeavoured to bring forward, 

 in addition to the arguments adduced by James Clark, other 

 and indeed more cogent reasons in favour of the correctness 

 of his conception. For this purpose he has, in the first place, 



* Proc. Linn. Soc. New South Wales, vol. ix. 2, p. 329. 

 t " Notes on the Embryology of Sponges," in Ann. & Mag. Nat. Hist. 

 1878, ser. 5, vol. ii. p. 139 ; and ' A Manual of the Infusoria,' 1880-81. 



