226 LIVERPOOL BIOLOGICAL SOCIETY. 



nuclei are small and not very conspicuous, apparently on 

 account of the opaque protoplasm of the cells. The nature 

 of these cells seems to be distinctly different from that of 

 the much smaller spindle-shaped cells described in Axi- 

 nella mammillata, n. sp. (page 211). In the latter species 

 the granules of the cells are distinctly spherical, clear, and 

 highly light-refracting. In Seiriola the granules are opaque, 

 and apparently of no definite outline. Further, in Axinella 

 the spindle-cells run in strands along the chief masses of 

 spicules, and suggest at once that they might be " sclero- 

 blasts." But in Seiriola such a relation between the 

 spindle-cells and the spicules does not seem to exist. 

 On the contrary, quite independently of the presence or 

 absence of spicules, the strands of those cells permeate 

 the choanosome in an irregular fashion, giving off numer- 

 ous branches (PL XIII., fig. 3). Further, I have not 

 been able to find any connection between those strands 

 and the incurrent and excurrent canals, or with any other 

 structure. Transverse sections through the strands are 

 frequently met with in preparations, and they show a 

 round outline. Sollas's "myocytes" seem to be similar 

 structures, but they differ from those cells in Seiriola 

 by chiefly occurring '' concentrically arranged about the 

 openings of the water-canals." Still I shall not be sur- 

 prised if future investigations prove those cells to be neuro- 

 muscular elements. 



In regard to the systematic position of Seiriola compact a 

 Professor Sollas wrote me as follows : — " The choano- 

 somal spicule is a characteristic oxyaster, the ectosomal 

 microsclere is a typical sanidaster ; this latter places the 

 sponge in the Sanidasterina. Of the genera of this group 

 it approaches most nearly Stri/phiua^, but differs from all 

 the species of this genus which I have seen. The sani- 

 daster is a better sanidaster, i.e., more typical and regular 



