BLACKMAX: THE SPERMATOGENESIS OF SCOLOPENDRA. 103 



cleavage spindle up to the eight-cell stage." On equally good ground . 

 Griffin ('99) decides that, in Thalassema and Zirphea, "the black focal 

 granule is functionally here the true ceutrosome, as understood by Boveri 

 — the single permanent cell organ, which forms the dynamic centre of the 

 cell and multiplies by division to form the daughter cells." A like posi- 

 tion is taken by Wheeler ('95, Myzostoma), Lillie ('98, Unio), Lin- 

 ville (:00, Limnaea), Coe ('99, Cerebratulus), and Kostanecki (:02, 

 Cerebratulus). 



In the sperm cells of insects it is not so difficult to locate the ceutro- 

 some, for there is at the centre of the aster (which is usually not well 

 developed) a simple granule toward which the rays converge. This 

 granule is, as a general thing, contained in no centrosphere or similar 

 structure, and hence is indubitably the centrosome. Such structures are 

 figured by the following authors : Platner ('86, Lepidoptera), Henkiug 

 ('91, Pyrrhocoris), Toyama ('94, Bombyx), vom Rath ('92, Gryllotalpa), 

 Montgomery ('98 to :01, Hemiptera), Paulmier ('99, Anasa), McClung 

 (:00 to :02 a , Acrididae, Locustidae), Sutton (:00, Brachystola), de Sinety 

 (:01 Orthoptera). 



On the other hand, Boveri's view that the inner zone is the centrosome 

 is supported by Fiirst ('98, Ascaris) and MacFarland ('97, Diaulula and 

 other gasteropods). The observations of Smallwood (:Ol) upon Bulla 

 would seem also to agree in some points. Wilson ('95 b , Toxopneustes), 

 and Conklin (:02, Crepidula) find a large reticular sphere at the centre 

 of the aster at certain stages, in which the homologue of the centrosome 

 is very hard to distinguish. In the early stages, however, Wilson finds 

 "one or two extremely minute granules (centrioles), which stain deep 

 blue in the haematoxylin," contained in an irregular mass which is 

 colored by the Congo red. He believes this mass with its centriole cor- 

 responds to Boveri's centrosome. In this paper Wilson concludes that 

 the central granule (" centriole ") " is formed endogenously in the central 

 mass." Such is certainly not the case in Scolopendra, where this central 

 mass or centrosome may be seen at all periods of the cell's development 

 and indeed is the only part of the structure at the centre of the radia- 

 tions which shows this Dersistenee. From the phenomena observed in 

 Scolopendra it would seem, on the contrary, that the centrosphere and 

 aster are rather exogenous formations brought about by the influence 

 which the centrosome exerts upon the archoplasm of the cell. 



In a later paper Wilson (:01 a ) states his belief that there are "good 

 bases for the conclusions that centriole, centrosome, and aster are but 

 concentric differentiations of a structure that is essentially a unit." 



