46 THALASSICOLLID.E. 



being aggregated round a blackish body placed in 

 the centre of the spherical mass. The dark cen- 

 tral body is found on examination to consist of 

 a strong elastic membrane, enclosing a pale 

 nucleus-like vesicle, embedded in a somewhat 

 peculiar granular substance. Numerous slender 

 branching ''fibrils" radiate through the gelati- 

 nous body from the interior of the dark central 



mass. 



In CollosphcB^^a the spicules are absent, but the 

 entire animal is enclosed in a transpai'ent, reticu- 

 lated, very brittle shell (d). 



From the preceding account it will be evident 

 that the Thalassicollidce differ essentially from the 

 other groups of Astomatous Protozoa, though they 

 at the same time present remarkable affinities to 

 more than one of these. Of their animal nature 

 no doubt can be entertained, notwithstanding the 

 assertion made by some that " they are referrible 

 rather to the Diatomacese," whilst others have de- 

 signated them " agglomerations of organised ra- 

 "phides, as it were, raised to the state of inde- 

 pendent beings." 



3. Acantliometree. — The curious Acantho- 

 metrcB of J. Miiller are closely allied to the pre- 

 ceding. Their peculiar, siliceous, radiating spines, 

 which meet in the centre of the gelatinous body 

 and project in most cases considerably beyond 

 its surface, will sufficiently serve to distinguish 

 them {fig. lo). Like the ThalassicollidcB, the 

 AcantJiometrcB are marine, and destitute of loco- 

 motive power. In size they are more minute. 

 It was proposed by Miiller to unite these animals 



