ZooL.— Vol. II.] RISEN— OLIGOCH.-ETA. 97 



may be seen one or more dark-staining dots, the centro- 

 somes, surrounded by a more or less diffused zone or 

 sphere, — the somosphere (Eisen 20). The latter is either 

 star-like, as in fig. 106, or well defined and spherical, as in 

 figs. 105 and 106. In some archosomes I have found two 

 separate somospheres, each with one or more centrosomes. 

 In fig. 107 one of the somospheres in a is much larger than 

 the other and contains two centrosomes connected by a 

 dark band. In the specimens from Tahiti, I have never 

 found a cell in which more than two archosomes could be 

 identified with certainty. Their position in the cell is very 

 constant, always below the nucleus, close to the central 

 cylinder of cytoplasm, which projects from the nucleus 

 downwards. In a specimen from Mexico, four or more 

 archosomes (Eisen 19) were found in some of the cells. 



The radiations which are frequently seen projecting from 

 the archosome and which are, sometimes, as clearly defined 

 as fibers are probably of strictly cytoplasmic nature and 

 possess, perhaps, the function of supporting the archosome. 

 As regards the other structures of these cells, I can add 

 but little to the previous descriptions. The cytoplasmic 

 agglomeration designated as otosome is easily fixed with cor- 

 rosive sublimate or alcohol, but not so well with other fixa- 

 tives. It cannot be demonstrated in every cell. The very 

 fine plates supporting the cytoplasmic cap above the nucleus 

 (fig. 98) are rarely satisfactorily stained except by the 

 Benda iron-hgematoxylin method. 



Finally, mention must be made of a most peculiar form 

 (fig. 100) of archosome which the author has observed 

 only a few times. Its shape is that of a long sausage-like 

 body of reticulated structure throughout, in which are seen 

 several dark-staining granules, especially at the poles. Its 

 location is always the same as that of the other archosomes, 

 among which it appears to be an unusual or abnormal form. 

 As regards earlier observations of the otosme, I find that Dr. 

 Horst (17) distinctly but faintly outlines this body (fig. 37, 

 Tab. IV,) but makes it appear as though connected with 

 a tube running between the cell and the cuticle. He does 

 not refer to it in the text. 



