20 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



centrosomes in staining reaction and in general shape and appearance. 

 When stained with iron-haeraatoxylin alone the only apparent differences 

 are in their irregular shape and indefinite position. But in slides where 

 the decolorizing has been carried farther than usual, these lose their black 

 stain, while the centrosomes retain their color much longer. Then, too, 

 in the double stain with Heidenhain's iron-haematoxylin and Congo red 

 the centrosomes stain an intense black, while the cytoplasmic granules 

 are of a brownish red color. 



As to the nature and function of the granules I can say nothing defi- 

 nite, but I consider it probable that they are metaplasm. This term as 

 generally used may, I believe, be applied to any lifeless substance found 

 in the protoplasm of the cell, and has often been used to designate both 

 reserve food-material and by-products or secretions of the cell which no 

 longer function in the cell's activity. That such is the nature of these 

 granules is indicated very strongly, although of course not proved, by the 

 fact that, during the active stages of the following mitoses, when all the 

 other constituents of the cell change in a greater or less degree, these 

 bodies remain passive in the cytoplasm and seem to undergo no change 

 whatever. This view is further strengthened by the fact that at various 

 places in the interstices between the membranes of adjacent cells there 

 are numerous aggregations of a substance similar in general appearance 

 and in staining reactions to these metaplasmic bodies. Their presence 

 outside the membrane offers no evidence as to whether they are excre- 

 tions or food material. It is probable, however, that both materials are 

 here represented, since there seems to be some diversity of staining 

 reaction and they vary much in size and general appearance. The larger 

 ones have much the appearance of oil droplets. They possess clear-cut 

 outlines and stain in the characteristic manner witli osmic acid, while the 

 smaller ones are more irregular in outline and stain differently. The 

 best proof of the oleaginous character of the larger ones is found in the 

 material fixed in Flemming's fluid. Here these bodies exhibit the reac- 

 tion so characteristic of fat droplets when treated with osmic acid. 



The cytoplasm near the cell membrane is considerably denser than 

 that occupying the rest of the cell. It seems here to form a layer, the 

 inner part of which is only a little more closely woven than is generally 

 the case in these cells. In this layer the cytoplasm, as one proceeds 

 outward, becomes more and more dense until at the periphery it forms 

 a structure which serves as the limiting membrane of the cell. It is 

 evident, I think, that in Scolopendra the cell membrane is but a slightly 

 modified thickening of the ordinary cytoplasm. Indeed this structure is 



