98 bulletin: museum of comparative zoology. 



Generally the leucocytes had a single sphere, even though more than 

 one nucleus may have been present. 



Vom Rath ('92) found amitotic conditions in the " Stiitzzellen " of 

 the testis of Gryllotalpa. He says, " Es gelang mir mehrfach in unmit- 

 telbarer Niihe der Kerne zwei winzige Centrosomen zu erkennen und 

 ebenso constatirte ich in seltenen Fallen bei eingeschntirten Kerneu 

 eine deutliche Strahlung um die beiden Centrosomen, die ofFenbar als 

 Attractionssphare bezeichnet werden muss" (p. 115). 



Van der Stricht ('92) showed the continuity of the attraction spheres 

 in the cleavage of Triton. He also showed that the centrosomes of 

 mitosis in cartilage cells of various vertebrates persist in the resting 

 cell. 



Brauer ('93, '93*) discovered the centrosome within the resting 

 nucleus of spermatocytes of Ascaris megalocephala univalens. Pre- 

 ceding a division of the cell, the centrosome divided while inside 

 the nucleus and the two resulting centrosomes migrated into the 

 cytoplasm. 



Moore ('93) described an archoplasm with a " central body," " me- 

 dullary zone " and radiations in resting cells of the undifferentiated 

 genital ridge of the larval salamander. The archoplasm gave rise to the 

 spindle of mitosis. In leucocytes of the larval salamander a similar 

 structure was found, instead of the simpler conditions described by 

 Flemmiug ('91). 



Vom Rath ('93) described attraction spheres and centrosomes in 

 various resting cells of Amphibia and studied the behavior of these 

 structures during amitosis of the sexual cells. The structures were 

 found also in the sexual cells of Astacus. 



Watase ('93, p. 442) concludes that " the centrosome is not a unique 

 oro-an of the cell, but is identical with the microsome which exists every- 

 where in the cytoplasm." 



Zimmermann ('93) described what he considered to be a modified 

 attraction sphere in pigment cells of teleosts. There is a very much 

 elongated " Centralstab," comparable to a centrosome, imbedded in a 

 correspondingly elongated " Archiplasm," whence proceed radiations. 

 In certain very large cells the radiations proceed from a " Centralnetz " 

 instead of from a " Centralstab." In the smaller cells a spherical 

 " Archiplasm " with radiations and a minute centrosome were present. 



Heidenhain ('94) investigated, in great detail, the conditions in leu- 

 cocytes and other cells of vertebrates. The " Microcentrum," which he 

 finds generally present, consists of two or three granules imbedded in an 



