Helen Dean Sing 367 
some and the angle of the loop indicating the place of their union. At 
a later stage the free ends of each loop become cemented together form- 
ing ring-shaped chromosomes. ‘* Hence in the typical chromosome of 
the ring form, the space enclosed by the chromosome is the space between 
two univalent chromosomes and has nothing to do with the longitudinal 
spht.” Montgomery asserts that the longitudinal splitting of the chromo- 
somes in preparation for the second maturation mitosis appears in the 
arms of the loops before the rings are formed, and that it has been over- 
looked by the other investigators, as it is completely hidden in the meta- 
phase and only reappears in the anaphase as a longitudinal splitting of 
the daughter chromosomes. Montgomery believes, therefore, that the 
so-called heterotypic division in the species of amphibians that have so 
far been investigated is a true reduction division in the Weismannian 
sense and that the second division only is a longitudinal one. He ven- 
tures the prediction that this will be found true for all forms in which 
the heterotypic division is found to occur. 
The interpretation given to the ring-formation by Montgomery has 
been criticised by Janssens and Dumez (25) who insist that in Pleth- 
odon both of the maturation divisions are longitudinal. Janssens (24), 
however, in a more recent paper dealing with the development of the 
spermatocytes of Batracoseps attenuatus, seems to have changed his 
former view as he states that “il est extrémement probable, pour ne pas 
dire plus, que les 12 anses du bouquet chez le Batracoseps résultent de 
la soudure deux a deux suivant toute leur longueur des 24 chromosomes 
des derniéres cinéses somatiques.” This conjugation of the chromosomes 
leads later to the formation of dyads “ qui seront séparées pendant le pre- 
miére cinése de maturation ou hétérotypie. I] est done trés probable que 
les deux spermatocytes II regoivent chacun 12 chromosomes entiers, ¢’est- 
a-dire la moitié des 24 chromosomes des derniéres cinéses spermato- 
goniales.” Besides supporting Montgomery’s contention that the first 
maturation division in the spermatocytes of amphibians is a reduction 
division, this work of Janssens is very valuable in another way, as it is 
the first work on the spermatogenesis of amphibians that suggests the 
possibility of a side by side union of the chromosomes during synapsis. 
I do not see why it is necessary to assume, as have the majority of the 
investigators on amphibian spermatogenesis, that the chromosomes 
must always unite end to end in synapsis. Evidence is not lacking that 
a conjugation of the chromosomes in pairs may take place previous to 
the first maturation division. Thus Riickert’s (49,50) early observations 
on the ovogenesis of Pristiurus seems to show a side by side union of the 
