THE SPERMATOGENESIS OF THE MYRIAPODS. 2O5 



As will be seen from the foregoing description, the tetrads 

 occurring in Scolopendra are similar to those previously described 

 by other authors in various arthropods. What may be taken as 

 the type of these figures was first reported by Paulmier, '99, in 

 Hemiptera and McClung, 'oo and '02, in Orthoptera. Structures 

 differing slightly in detail, the apparent divergence evidently 

 being due more to interpretation than to any essential morpho- 

 logical variations, have been found in other arthropods by Henk- 

 ing, '91 (Pyrrhocoris), Vom Rath, '95, '97 (Gryllotalpd), Toyama, 



FIG. 15. X i,44O dia. Nucleus of first spermatocyte during late prophase, show- 

 ing various modifications in the shape of the chromosomes at this time. The acces- 

 sory chromosome is seen to be split longitudinally. Centrosomes with well-developed 

 astral rays at opposite poles of the nucleus. 



'94 (silkworm), Riickert, '95 (Copepoda), Montgomery, 1 '98, 'oo, 

 'oi (Hemiptera, Pcripatus], Blackman, 'oi (Scolopcndni), P. Bouin, 

 '02 (Lithobius), Miss Nichols, '02 (Oniscus], and others. In the 

 tetrads observed by all of these authors, the cleavages universally 

 represent a longitudinal and a transverse division of the double or 

 bivalent chromosome of the spermatocyte. Apparent discrep- 

 ancies are undoubtedly due to mere variations in detail or differ- 

 ences in interpretation and denote no real important divergence 

 in the formation of the tetrads. 



1 In his earlier paper Montgomery reported two cross divisions as occurring in 

 Pentatoma (ut-/n's/us), but in his subsequent publications has denied the accuracy 

 of this observation and now believes that one longitudinal division invariably occurs. 



