THE SPERMATOGENESIS OF LEPIDOSIREN PARAHOXA. 13 
fusion seems to be completed, at any rate over the polar 
hemisphere. Each pachytene thread now appears as a single 
band, with a pronounced beaded appearance. 
It is still impossible to count the number of complete 
threads in the nucleus owing to their large number and great 
length, and in most nuclei the onset of synizesis at about this 
stage renders it impossible to do so until the diakinetic 
chromosomes make their appearance. I found one nucleus, 
however, fig'ured in PI. 2, fig. 1 5, which has obviously remained 
in the bouquet stage for a longer period than usual, aud 
consequently the shortening of the chromosomes (which 
proceeds continuously during the whole of the prophase till 
the disappearance of the nuclear membrane) allows of an 
approximate count of the pachytene loops being made. This 
nucleus, which is intact in a 40 jx celloidin section, was drawn 
from both sides and the number of free ends directed towards 
the pole was counted. In the figure only the superficial 
chromatin of the upper half of the nucleus is shown, but 
owing to the pole being slightly tilted up far more than half 
the total number of free ends are shown. From the exami- 
nation of this nucleus from both sides, I can say with certainty 
that there are rather less than thirty-eight free ends directed 
towards the pole. As the great majority of the chromosomes, 
as in the bouquet stages of other forms, are in the form of 
horse-shoe-shaped loops with two free ends, it is quite certain 
that the loops are in the reduced number, that is nineteen. 
This is in accordance with what we know of the bouquet 
stage in other forms. The loops have been found to be 
present in half the somatic number in all those species in 
which, owing to the small number of the chromosomes, it has 
been possible to count them at this stage. Gregoire (1910) 
gives the following list of such forms: Amphibia (all since 
Flemming up to the most recent workers), Tomopteris 
(Schreiner), Cyclops strenuus (Lerat), Pedicel lin a 
(Dublin), Ophryotrocha (Gregoire and Deton, Schreiner), 
Thy sanozoon (Deton), As car is (Griggs), Zoogonus 
(Gregoire). To this list, which could certainly be much 
