AND THALASSICOLLA. 73 



colla. The former name was applied, in 1834, by Meyen to 

 a form of agastric animal, which he descrihes as a spherical, 

 muco-gelatinous mass, constituted internally of globules, which 

 again consist of vesicles. This genus, although Meyen's 

 description is not quite accurate, would clearly appear from 

 his figure, according to Prof. Miiller, to be identical with the 

 Thalassicolla of Huxley. 



Prof. Miiller then proceeds to describe and discuss the 

 structure and varieties of the different forms assembled by 

 common characters under this generic group, and fully con- 

 firms in every particular the description given by Mr. Huxley. 

 But he is disposed to subdivide the Thalassicolla of that 

 observer into two sub-genera, and adds an account of other 

 specific forms. One subdivision of the group, for which he 

 would retain the term Sphcsrozotcm, Meyen, on account of its 

 priority, would include SphcBrozoum (^Thalassicolla) fuscum, 

 Meyen, and S. ( T.) punctata, Huxley, and a minute descrip- 

 tion of their structure is given. 



A second form, noticed by Mr. Huxley as a variety of 

 T. punctata, and characterized by its containing in the centre 

 a prismatic crystal, or crystals, and having a fenestrated 

 shell not unlike that of a Polycystiaa, Ehr., he erects into the 

 type of a distinct genus or sub-genus with the name of Collo- 

 sphcera, assigning to it the specific designation of C Huxleyi. 



In his description of the structure, which corresponds fully 

 with that of Mr. Huxley, he lays particular stress upon the 

 nature of the crystals contained in the large cells. These are 

 sometimes present in small, sometimes in considerable num- 

 ber, and in one case he counted twenty-seven in a single cell. 

 They are about 1-60" in length, clear and colourless, and 

 from their form, together with their insolubility, of a nature 

 altogether unusual in organized bodies. They are rhombic 

 prisms, belonging to the two-and-two-membered system, with 

 four-sided summits and a greater or less truncation of the 

 acute, long angle of the prism. Upon measurement of the 

 angles, which from the size of the crystals was not very 

 easily taken, it appeared that the crystalline form agreed in 

 a very remarkable manner with that of the sulphates of 

 strontian and of barytes. Their chemical properties, also, 

 which are described, would indicate that they were composed 

 of a difficultly soluble earthy sulphate, which, however, 

 could not be that of lime. And although strontian and barytes 

 have not been observed in sea-water, the presence of the latter 

 earth therein may be surmised from the circumstance that 

 celestine is met witii in the fossiliferous marine deposits, in 

 the muschelkalk, lias, cretaceous and tertiary formations. 



