96 bulletin: museum of comparative zoology. 



two apparently longitudinal cleavages of the chromosomes. This view- 

 is supported by the observations of the following : Moore ('95) on 

 elasmobranohs ; Flemming ('87), Meves ('96), Carnoy et Lebrun 

 ('98), McGregor ('99), Eisen (:00), Kingsbury (:02), Janssens (:Ol) 

 on Amphibia; Lenhossek ('97), and Hermann ('89) on mammals, 

 while it is opposed by those of very few authors indeed. 



Montgomery (:03), following out the suggestion of Fick ('93), has 

 demonstrated that in Plethodon and Desmognathus one of these divi- 

 sions, while apparently longitudinal, accomplishes the same result as 

 does the transverse division in invertebrates, i. e. the separation of entire 

 spermatogonial chromosomes at the point where they united in the pre- 

 ceding synapsis. Thus the union of the chromosomes of vertebrates 

 during synapsis is, in effect at least, a side to side union as dis- 

 tinguished from the end to end union characteristic of invertebrates. 



In invertebrates — if we exclude Ascaris, which, on account of the 

 nature of the chromatin bodies, naturally undergoes different changes — 

 reduction is accomplished by one longitudinal and one cross division of 

 the chromatin filament of the prophase. In this conclusion the following 

 investigators agree: in Arthropoda Henking ('91), vom Rath ('92, 

 '95), Toyama ('94), Puickert ('95), Paulmier, ('98, '99), Montgomery * 

 ('98 c , :00, :Ol), McClung (:00, :02 b ), Blackman (:01, :03), P. Bouin 

 (:03), and P. et M. Bouin (:02) ; in Mollusca Lee ('97), Griffin ('99), 

 Linville (:00), Lillie (:Ol) ; in lower invertebrates Klhickowstrom ('97), 

 Francotte ('97), van der Stricht ('96), and Griffin ('99). 



The only investigators with whose work I am acquainted who oppose 

 this view are : Wilcox ('95), Brauer ('92), and de Sinety (:Ol), and the 

 work of these three investigators has been discredited by other observa- 

 tions upon the same or closely allied materials. Wilcox asserts that 

 the two spermatocyte mitoses accomplish a double transverse division 

 of the chromosomes. Such is not the case in the western individuals of 

 the same species, in which a longitudinal, followed by a transverse, 

 division invariably occurs. De Sinety, working upon the cells of 

 several genera of Orthoptera, asserts that the two divisions are longi- 

 tudinal. This also appears to be a mistaken conception, as pointed out 

 by McClung (:02 lj ). Appearances, which upon superficial examination 

 might lead to this view, are occasionally met with in orthopteran mate- 



1 In an earlier paper Montgomery reported the occurrence of two cross divisions 

 as universal, but in his subsequent articles he has entirely withdrawn this state- 

 ment, and now believes that reduction is always accomplished by one longitudinal 

 and one cross division. 



