SYNCRTPTA SPONGIARUM. 313 



(in preservation) yellow spherical "alga?" found in sponge-mesogloea are the 

 alternate generation of Syncrypta spongiarum, it seems possible that the 

 unusually small size of this species among its allies may have been developed 

 with the advantage of enabling the monads to enter the prosopyles of sponge- 

 chambers, and so be ingested and pass into the tissues of its host. From 

 Polejaeff's plate f>, the prosopyles of his Cacospongia and Carteriospongia 

 are mostly about 3 /j, in diameter ; a monad of 2'2 diameter is therefore very 

 closely the largest size which can be sure of entering the apertures of the 

 screens which protect its prey. 



It is noticeable that in fresh water, Pascher (1910, p. 37) finds Syncrypta 

 volvox only frequent in spring (April) and September, more rare in the 

 summer. This allows the inference that the months of greatest sunshine are 

 passed in a more important Palmella stage. 



