ROBERTSON : THE CHROMOSOME COMPLEX. 291 



STRBULA ADMIRARir.IS. 



what similar to what Sutton ('00) describes for Brachystola. 

 S. admirabilis (figs. 7, 8 and 9) agrees with this, but we fail 

 to find that "when the nuclear membrane has completely dis- 

 solved away this single loop" (spireme) "segments into two." 

 In his figure 6 it does not seem to me that he has furnished 

 conclusive evidence that his N2 elements are two heterochro- 

 mosomes. How can he say for sure that both are heterochro- 

 mosomes? One may be, but it is a certainty that they both 

 resemble very much some of the other chromosomes. Had he 

 shown the full number of the complex here, the number which 

 he claims for the species, and had proven beyond a doubt that 

 the number was even, not odd, his guess might have had some 

 weight, but he has not shown the whole number in this par- 

 ticular cell nor has he convinced us that the number in the 

 spermatogonia is even. His N2 pair looks very much like the 

 No. 6's or No. 7's of admirabilis. Of course, he claims to find 

 an even number in the metaphase of the spermatogonia, but 

 his two drawings do not furnish sufficient evidence to justify 

 us in accepting this point as proven, especially since it must 

 be accepted in the face of all the other evidence in the family, 

 which in every case happens to be to the contrary. Follow- 

 ing out the reasoning, he concludes that each "first spermato- 

 cyte receives a half of each of the two heterochromosomes" 

 as well as a half of all the others. 



In the reconstitution of the nucleus he again finds that when 

 the "chromosomes begin to elongate and loosen up, two of 

 them do not undergo these changes but remain smooth and 

 dense" (cf. his fig. 13). These he considers identical with his 

 N2 elements of the spermatogonia. The strange thing, how- 

 ever, is that in his figure 14 the two heterochromosomes should 

 suddenly conjugate and there should appear immediately 

 thereupon, seemingly in the place of one of them, the single 

 nucleolar structure N. If these heterochromosomes are to 

 conjugate he should have found previous to his figure 14 three 

 bodies, two heterochromosomes and a nucleolus in each nu- 

 cleus. According to his figures there were only two bodies at 

 first, the heterochromosomes, and after the conjugation of 

 these there were two bodies still. There seems to be some- 

 thing wrong here, for it is improbable that a nucleolus would 

 appear so suddenly as his element N. It must have been pres- 

 ent before. And in addition to this, if his heterochromosomes 



