Zool.— Vol. I.] EISEN—PLASMOCYTES. 1 5 



among the latter we meet with all stages of development 

 and dissolution; development as regards the cytoplasm, dis- 

 solution as regards the nucleus. 



A fusiform corpuscle of the blood of Batrachoseps, if 

 stained with toluidine, pure and simple, presents the following 

 structure : A large central nucleus of rather irregular, ob- 

 long form, the two longer sides being always convex, while 

 the two short sides are generally flat, or even concave, each 

 one furnished with a dell. The nucleus itself requires little 

 description, as it is always in a state of rapid dissolution. 

 We find nuclei in all the various stages, some showing 

 a distinct network with fairly well defined chromosomes, 

 others again with only a diffuse mass of ill defined granules. 

 In all the figures given I have, therefore, in no way en- 

 deavored to reproduce a copy of the nuclear structure, but 

 only to show its general form and appearance, the minute 

 details being entirely unimportant. 



What attracts us the most in the fusiform corpuscle is the 

 cytoplasmic element which adheres to the nucleus, princi- 

 pally at one, but frequently at both of the poles, some- 

 times, also, as a very thin coating on its long sides. Not 

 only is this cytoplasmic coat thicker at the poles than on the 

 long sides, but the structure of the polar parts is entirely 

 different from that which adheres to the long sides. These 

 sides are covered by a very thin layer of faintly staining 

 cytoplasm. In some corpuscles this layer can be observed 

 without difficulty all around the nucleus, while in others 

 it becomes, at the middle of the long sides, so thin that 

 it is hardly to be observed, and in some instances prob- 

 ably it is entirely absent. The latter appears to be the rule 

 rather than the exception. More rarely this layer is suffi- 

 ciently thick to allow us to define it in two separate layers 

 of about equal thickness, as, for instance, seen in figs. 

 21 and 27; but at the poles, or at least at one of the poles, 

 this cytoplasm is greatly increased in size, showing that it 

 consists of a number of distinctly staining and differentiating 

 zones or spheres. The toluidine has a marked and distinct 

 affinity for this part of the corpuscle, and stains it in a way 



