No. 3-] MORPHOLOGY OF THE STENTORS. 479 



A. Anatomy. 



The recent careful study of the external anatomy and the 

 fission of the Blue Stentor by Schuberg ('90) added very much 

 to our stock of information regarding this form. I have re- 

 investigated every structure described by him, and our results 

 coincide in nearly every particular. But, in regard to fission, 

 our observations are at variance on one or two important 

 points. I have been able, furthermore, to add a few details 

 to our knowledge of this important process, especially in 

 regard to the nuclear changes, which hitherto have received 

 less attention than the cytoplasmic phenomena of fission. 



I . EctO' and Endoplasm. 



Just as the fundamental Metazoan body has two cell-layers 

 differing in function, so the unicellular body of a Protozoon is 

 susceptible of division into two layers, ectoplasm and endo- 

 plasm. This division is by no means artificial, but is based 

 upon a difference in structure and function. The differentia- 

 tion of the two layers is not so conspicuous among the Infu- 

 soria as with the Rhizopods, mainly on account of the relatively 

 extreme thinness of the ectoplasm, much the greater bulk 

 of the cytosome being endoplasm. There is, besides, often an 

 absence of delimitation between the ectoplasm and endoplasm. 

 Such is the case with Stentor, where, however, the presence 

 of ectoplasmic pigment, or of zoochlorellae limited strictly to the 

 endoplasm, often helps to define the two. In .S. cceruletis the 

 ectoplasm contains abundant pigment, arranged in definite 

 longitudinal bands, the "blue," or "granular" stripes (" Rippen- 

 streifen " of Biitschli). Implanted in its substance are the 

 contractile threads and the "roots" of the cilia. It is pierced 

 by the basal plates of the membranellae, which pass through 

 it and some distance into the endoplasm. It is of denser 

 structure and of a firmer consistence than the endoplasm. 



An alveolar layer of the ectoplasm has been demonstrated by 

 Bijtschli, Schuberg, Schewiakoff and others in many Infusoria, 

 both holotrichous and heterotrichous. If such a layer exists 

 in Stentor, as seems probable, it is extremely thin, and its 



