Studies on Synapsis. 



65 



who have studied the interkinetic nucleus of late years agree that there is 

 no loss of individuality in the " spirophase," the precise details of the process 

 do not appear to be universally alike. In view of the importance attributed 

 in Morgan's suggestive speculations to the linear alignment of the chromo- 

 sojue segments, it is tempting to seek for an interpretation of the spirophase 

 in other forms along lines similar to those indicated above. But at present 

 there is no justification for doing so. ^ 



There seem to be at least two distinct types of nuclear organisation in the 

 resting stage. The first may be termed the unit-reticula-complex ; in this 

 case the telophasic chromosomes become increasingly vacuolated, until the 

 spongy cylinders so formed cannot be distinguished, This at least is 

 certainly the case in certain Orthoptera (ef. of Mohr, Buchner, et al.), 

 where the individual reticula of the telophase chromosomes are separately 

 invested in their own membranes ; it is also the only possible interpretation 

 of the diffuse stage in the oocyte.* The second type of resting nucleus is 

 that to which the term spirophase was applied by Bolles Lee, 1912 (9), as the 

 result of his very important work on Paris qtutdrifolia. With the exception 

 of Dehorne, 1911 (10), workers of animal cells are agreed that there is no 

 cleavage in the telophase threads ; many botanical cytologists like Fraser, 

 1912 (11), and more recently Digby, adhere to the belief that the cleavage, 

 which becomes manifest at one mitosis, begins in the anaphase or telophase 

 of the preceding mitosis ; but others, like Gates, 1912 (12) and Bolles Lee, 

 find no evidence of preparation for the ensuing division until the prophase 

 itself. One thing is evident in any case : the prodigious heterogeneity of 

 structure of the chromosomes in the interkinesis as contrasted with their 

 visible compactness of structure in the metaphase. And this should be 

 borne in mind in reference to certain criticism which has been raised in 

 reference to Morgan's hypothesis by Prof. Bateson in his recent Croonian 

 Lecture. 



The Meiotic Phase in the Male Germ Cells. 



Lefevre and McGill do not give details respecting the initial processes 

 during the synaptic periodf in the primary spermatocytes of Anax. In the 

 case of Sympetrum and L. basalts, Smith records the formation of leptotene 

 filaments from irregular blocks of chromotin, as in Oncopeltus and Lygaeus 

 (Wilson), following on a short reticulate phase. In no preparations of 



* Except pertaps in Hi/menoptem parasitica (Hogben). 



t American authors use the term " growth period " more conveniently applicable to 

 the period when the oocyte grows in cytoplasmic bulk and yolk deposition occurs. 

 " Maturation prophase " is better restricted for the formation of the definitive tetrads, 

 especially in view of the telophasic significance of the earlier events. " Meiotic phase" 

 includes both reduction divisions. Hence the use of a special term. 



