354 THE PLANKTON OF THE FARoE CHAXKEL AND SHETLANDS. 



lined with a continuous layer of polygonal areas, and perforated by 

 numerous pores. In the centre of the capsule is a rounded nucleus, 

 which, as Hertwig remarks, is easily shelled out of the capsule by 

 pressure, owing to its thick wall. 



The contents of the central capsule are rounded bodies of various 

 constitution, some containing oil drops, some granular protoplasm, others 

 pale and clear, and oil drops of varying size, some few of which are large 

 and of cinnamon colour. Xumerous vacuoles occur, large and small. 



The nucleus has an investing membrane sufficiently dense to allow 

 of its being readily shelled out of the central capsule on pressure. It 

 is closely packed with small round cell-like bodies, amongst which are 

 some large oval, or ellipsoidal, nucleated bodies. The colour of the 

 nucleus is yellow. Diameter of the calymma, 3-4 mm. ; of the central 

 capsule, 1-1 mm.; of the nucleus, -05 mm. 



2. Thalassicolla pelagica (Haeckel, Die Radiolarien, 1862). 



This species is distinguished by the small size of the central capsule 

 in comparison with the calymma, the pellucid appearance of the latter, 

 the small amount of pigment, and pale white or yellowish white colour 

 of the central capsule. The jelly of the calymma is much less firm 

 and consistent than that of Tli. nudenia, and the pigment is much 

 less distributed in strands through the calymma than in the latter, 

 and is nearly entirely grouped round the central capsule. The 

 membrane surrounding the central capsule is thin, and though marked 

 with very close dots (pores), does not possess the polygonal cell area 

 markings of Th. nucleata. 



The contents of the central capsule are small, round bodies, packed 

 densely between which are many small oil globules, but the latter 

 are grouped into larger drops chiefly round the outer rim of the central 

 capsule and within the central capsular membrane. Between the 

 intracapsular bodies are many small vacuoles, often containing small 

 oil drops. 



The nucleus has a fine and porous investing membrane, and is 

 papillated with irregular-shaped protuberances about as long as the 

 radius, and there are a few long, tube-like or vermiform bodies. The 

 rest of the contents of the nucleus appears to be made up of small 

 rounded bodies, between which are spaces resembling vacuoles. 

 Diameter of the calymma, about 3-4 mm. ; of the central capsule, 

 0-4-0-6 mm. ; of the nucleus, -02 mm. 



The third kind of Thalassicolla possesses a remarkable central 

 capsule, and it has been suggested to me that it should be referred 

 to a new genus, for which the term Thalassiosolen is proposed. 



