SCHIZOPORELLA HYALINA. 275 



The most interesting point in the history of this com- 

 mon and widely spread species is the mode in which the 

 ovicelligerous cells are developed. Universally, it would 

 seem, in the common form, the ovicells are produced, not 

 on the primary perfect zooecia, but on special rudi- 

 mentary cells, which originate on the upper surface of 

 the former, and are intercalated between them, at the 

 oral extremity. 



These ovicelligerous cells are wedge-shaped, and of very 

 small size, and fit into the space that separates the zooecia 

 at their upper end. They are aggregated in the central 

 portion of the colony, where they occur in great numbers, 

 and give the crowded and ' ' heaped " appearance so cha- 

 racteristic of the species in its adult condition. Amongst 

 the ovicelligerous cells there are usually many cells of 

 normal form, but small size, frequently extremely diminu- 

 tive, developed, like the former, upon the primitive layer, 

 and constituting an upper stratum. As I have said, the 

 mass of ovicelligerous and other secondary cells is con- 

 fined to the centre of the colony; and surrounding it 

 there is generally a broad tract occupied by the subcylin- 

 drical cells, lying horizontally and regularly disposed, 

 and forming a glittering belt round the opaque central 

 nucleus*. 



The ovicelligerous cells of S. hyalina derive an addi- 

 tional interest from the close resemblance which they bear 

 to the curious structures that frequently occur on the 

 front of the zoo3cia in S. linearis. The chief difference 

 between them lies in the more rudimentary condition of 

 the cell in the latter. 



* " Limbum quani ratliatum fanunt." Orim FABRIC-ITS. 



r '' 



