SPERMATOGENESIS OF SQUILLA ORATORIA 315 
Hermann’s fluid, stained with iron-hematoxylin and extracted 
fairly sufficiently, a longitudinal split is very clearly observable 
in each thread (fig. 13). In the pachytene stage the threads 
often present a distinct bouquet-like arrangement, most of them 
in the form of a complete loop, being arranged around a center of 
grouping, where they fuse with each other (fig. 14). No ac- 
counts of such peculiar arrangement of pachytene threads are 
found in Fasten’s two papers nor in Nichols’s description of the 
synizesis of Homarus and Hippa. But the latter author’s 
account (’09) of the corresponding stage of Idotea and Tal- 
orchestia apparently indicates the occurrence of such arrange- 
ment. Binford’s figures 10 and 11 also show the similar feature. 
As the nucleus passes from the leptotene to the pachytene 
stage, the size of both the nucleus and the entire cell increases 
considerably. In the pachytene stage, which lasts for a toler- 
ably long time, the nucleus and the cell continue to grow in 
some measure. 
I could not determine the precise procedure by which each 
pachytene thread is transformed into a tetrad; I shall accord- 
ingly confine myself to a few remarks on my figures 15 to 17, 
which I believe to exhibit some of the successive steps passed by 
the threads during the change in question. In figure 15 the 
nucleus contains several figures, many of which are in the shape 
of U or V, both arms consisting of two longitudinal halves. In 
the next figure (fig. 16), most of these U’s and V’s have been 
transformed into hollow squares, probably by opening out of 
the longitudinal halves of individual arms. Lastly, in figure 17, 
the nucleus encloses rings, crosses, rods, and the like, indicating 
that the formation of tetrads has been completed. Without 
question, every variety of the tetrads has arisen from those 
squares shown above. The above observation on the tetrad 
formation, fragmental as it is, suggests the occurrence of more 
complicate processes, such as are clearly demonstrated by 
Wilson (712), Montgomery (’11), and Wenrich (716) in the 
spermatogenesis of some insects. 
All the tetrads soon condense into rod-, dumb-bell- or crescent- 
shaped chromosomes, which are located mostly in the superficial 
