STRUCTUKE OP THE LARVA OP SPONGILLA LAOUSTRIS. 367 



Noldeke described the larva as consisting of " ectoderm " 

 (flagellated layer) and ''entoderm" (all the inner mass). He 

 agreed with Delage that the flagellated cells pass into the 

 interior and are taken in by the amoeboid cells, but he diff"ers 

 from him in stating tliat they are completely digested, and not 

 set free again to form collar-cells. He therefore follows Gotte 

 in describing the whole sponge as being developed from tlie 

 cells of the " entoderm/^ but he derives the chambers either 

 from a single cell or by the coming together of cells. 



B. Summary of the Author's Results. 



This brief account is introduced here with the object of 

 making it easier for the general reader to grasp the results, 

 and in order to emphasise the main facts brought out by ray 

 investigations ; in the first place as regards the histology of 

 the larva, and in the second place as regards its metamor- 

 phosis and subsequent development. 



(a) Histology of the Larva. — The free-swimming larva 

 is egg-shaped, with a broader anterior and a narrower posterior 

 pole. The surface of the body is covered all over with a uniform 

 layer of flagella. At the anterior pole is lodged the larval 

 cavity, while the posterior pole is a solid mass of cells. 



In the histological composition of the larva we can dis- 

 tinguish — 



(1) A layer of flagellated cells at the surface. 



(2) The inner mass. 



(1) The flagellated cells are arranged in a complete 

 layer over the whole surface of the larva, and are uniform in 

 character. Each cell carries a flagellum, which can be traced 

 down to the nucleus. The cell body is elongated and some- 

 what constricted in the vicinity of the nucleuSj which is onion- 

 shaped, and situated at the base of the cell (PI. 35 ; fig. 29 a, 

 PI. 40, &c.). 



(2) The inner mass may consist of as many as three 

 kinds of cell elements, of which two at least are always 

 present. 



(a) Cells with granular nuclei, always present as an irregular 



