BIGELOW: NUCLEAR CYCLE OF GONIONEMUS MURBACHII. 3G9 



a phenomenon of the same sort. But his account is not sufficiently de- 

 tailed to indicate conclusively whether or not the contraction stages in 

 Hydra are a normal part of the prophase. In view of these conflicting 

 results I agree with Gregoire ( : 05, p. 296), that Hydra merits a fresh 

 examination. 



Similar contraction phases are common in the spermatogenesis and 

 oogenesis of the higher Metazoa ; thus they have been described in 

 Ascaris (Brauer, '93, Sabaschnikoff, '97, Tretjakoff, :04), Lumbricus 

 (Calkins, '95), copepods (Hacker, '92 a , Rtlckert, '94. Lerat, :05), ostracods 

 ("Woltereck, '98), Protracheata (Montgomery, .00), insects (Henking, 

 '91, Montgomery, '98*, Paulmier, '99, and others), molluscs (Lee, '97), 

 and in vertebrates (Moore, '95, Meves, '96, McGregor, '99, Eisen : 00) ; 

 likewise in the flowering plants (Sargant, '96). 



Most investigators, following Moore ('95), have believed that numeri- 

 cal reduction of the chromosomes takes place during this condensation, 

 but others — the most prominent being Lee ('97), McClung ( : 02'\ 

 :02 b ), and within the last year, Tellyschinczky (:05) — have maintained 

 that these contraction phases are of purely pathologic nature, the con- 

 densation being in no way connected with synapsis. Tellyschinczky's 

 results are especially important, since the material he used was the living 

 cells from the testis of Salamandra, which he was able to study under 

 the highest powers. Lee, moreover, was able to follow in Helix the 

 actual formation of the "synapsis" artifact on living and slowly dying 

 cells. Opinion, then, as to whether contraction stages are normal or 

 artificial, is divided. 



The fact that in Gonionemus and Helix they seem to be artificial is 

 no conclusive argument that they need be so regarded in other forms. 

 In all these cases, however, so far as I am aware, the same phenomenon 

 of the " emptiness " of the nucleus accompanies the contraction phases. 

 If we imagine the chromatin strands in Gonionemus as beiug under ten- 

 sion and ready to contract under the slightest stimulus, we need go but 

 one step further to explain the situation in those forms, such as Ascaris 

 and elasmobranchs, where the tension is so great that the contraction 

 takes place without the necessity of an external stimulus. McClung's 

 general contention, that such contraction phases are in all cases purely 

 abnormal, seems to me unwarranted, although I agree with him, that too 

 much stress has often been laid on the contraction as an essential feature 

 of synapsis. 



The most fundamental question in this connection is, whether in Goni- 

 onemus there is a true synapsis or pairing of the individual chromosomes ; 



VOL. XLT1II. — no. 4 21 



