of the Sponges to the Choanqflagellata. 369 



refute both of them, and to prove that the whole process 

 which has hitherto been generally regarded as egg-segmenta- 

 tion, larva-formation, and metamorphosis, is nothing but an 

 organic process of multiplication, exactly agreeing with those 

 processes which have been recognized in various Flagellata. 

 With this view he endeavours, in the first place, to demon- 

 strate the agreement of the process of segmentation of the 

 Q^g, observed in many Sponges, with that division of a simple 

 Flagellate animal which leads to the formation of a consider- 

 able number of equivalent individuals, that is to say, to the 

 formation of a colony, appealing to the descriptions given by 

 Ehrenberg, Perty, and Schneider of the propagation of Poly- 

 toma uvella, by Dollinger and Drysdale of the division of a 

 Monadine, Heteromita uncinata, and by Hackel of the re- 

 productive cycle of his Magosphcera planula, and further 

 adducing the results of his own observations upon the propa- 

 gation of a Choanoflagellate, Salpingoeca fusiformis, newly 

 discovered by him. In this last organism he was able to 

 ascertain that a typically constructed individual animal be- 

 came transformed within its vase-like case, after the retraction 

 of the collar and flagellum, in the first place into an amoeba- 

 like body. After this had passed through a resting-stage 

 in the spherical form it underwent a regular division, the 

 final products of which quitted the capsule as flagelliferous 

 swarmers. From each swarmer a Salpingoeca fusiformis was 

 again produced. 



Placing this process side by side with the egg-formation, 

 segmentation, larval development, and metamorphosis of the 

 Sponges, Saville Kent formed the following conception of the 

 latter. From a simple collared cell proceeds a cell capable of 

 amoeboid movements. This, by continual binary division, 

 undergoes a segmentation like that of Salpingosca fusiformis } 

 and the final product in this, as in that case, is a considerable 

 number of cells, which in the first place have only a flagellum, 

 but subsequently acquire a collar, and so become collared cells, 

 whether they constitute together a free swarm -larva (swarm- 

 gemmule) or the collared-cell-layer of a flagellate chamber. 



As an essential distinction Saville Kent then indicated only 

 the circumstance that in the Sponges the individual animals 

 produced by division remain united (either as a swarm-gem- 

 mule or as the lining of a chamber) and produce (in the case 

 of the swarm-gemmule after attachment) a gelatinous basis, 

 upon which they are then seated in a continuous layer or in 

 groups ; while the Choanoflagellata do not possess any such 

 common gelatinous supporting substance. 



But even this difference Saville Kent thought he got rid 



