100 bulletin: museum of comparative zoology. 



concludes " dass eine Theilung der Attractionssphare bei der Amitose 

 stattfinden kanu . • . ; ob sie aber immer stattfiudeu muss, ist 

 uuwahrscheinlich" (p. 61). 



Von Erlanger ('96) observed the centrosome in resting epithelial 

 cells of salamander larvse. There were always two, connected by a 

 band of substance. In mitosis these centrosomes moved apart and the 

 spindle formed between them. In another paper ('96") he describes a 

 "Nebenkern" in resting sperm cells of the earthworm. In rare cases 

 a central granule and weak radiations were present. He believed the 

 structure to be archoplasm and centrosome. 



Meves ('96), in the spermatogonia of the salamander, found the 

 spheres of adjacent cells connected by bands of substance which are 

 probably remnants of the spindle. 



Ballowitz ('97*) demonstrated the centrosome and sphere in the cells 

 of the pharyngeal and cloacal epithelium of Salpa, without the use of 

 stains. The material was fixed in either weak or strong Flemming's 

 fluid, sublimate, or acetic-sublimate, and examined in water. The nu- 

 clei are sickle-shaped, and in the concavity of each could be seen the 

 large sphere which Ballowitz had previously described ('97). A de- 

 tailed study of the epithelial cells of Salpa appeared in a later paper 

 ('98'). The centrosomes were best seen in the unstained Flemming's 

 preparations. At the centre of the sphere were generally two, but 

 sometimes three or four, very highly refractive bodies. They often 

 appeared to be irregularly shaped or elongated, instead of spherical 

 granules. Ballowitz concludes " dass es zum Nachweise der Centro- 

 somen nicht immer einer specifischen Farbung bedarf, dass diese wich- 

 tigen Zellbestandtheile vielmehr auch in ungefarbtem Zustande in Folge 

 ihres charakteristischen starken Lichtbrechungsvermogens so sharf be- 

 grenzt hervortreten, dass sie leicht und sicher in der Sphare erkannt 

 und unterschieden werden konnen " (p. 358). 



Ballowitz believes the sphere and centrosomes to be present also in 

 the epidermal cells of Amphioxus larvse ('98). These cells have nuclei 

 varying in form from those that are deeply invaginated to those that are 

 sickle-shaped or complete rings. 



Eisen ('97) described a new element found by him in the blood of 

 some amphibians, reptiles, and man. To this element he gave the 

 name of " plasmocyte." He attempts to show that the plasmocytes 

 "are composed of the centrosomes and archoplasm (with part of the 

 cytoplasm) of the nucleated erythrocytes, . . . surviving in the blood 

 serum as free and independent elements capable of growth through 



