GERM CELLS OF ANURANS 251 
Shortly after their formation the leptotene threads tend to show 
a definite orientation of their free ends toward the centrosome 
and sphere in many cells, giving the appearance of a series of 
delicate loops. Janssens ('05) has characterized this orientation 
as the bouquet grele or leptotene bouquet. The chromatin por- 
tion of the looped threads is in the form of very minute particles 
distributed at more or less regular intervals along a central linin 
core or fibril. Usually at this stage one or more nucleoli are pres- 
ent, though they differ from ordinar}^ nucleoli in being in intimate 
connection with the chromosomes. These bodies have been 
termed chromoplasts by Eisen ('00), who first studied them in 
Batracoseps. We shall have more to say about these bodies 
later (figs. 10 and 55). 
Following the period of the leptotene bouquet, there occurs in 
amphibians an extremely important and interesting stage, first 
observed by Janssens ('05) and named by him amphitene. This 
stage marks the first formation of the thickened pachytene thread 
and corresponds to the zygotene of Gregoire's ('07) terminology. 
In Rana catesbeiana larvae the amphitene constitutes a very defi- 
nite and well-marked period in the maturation process — one that is 
easily differentiated from the leptotene preceding or the pachy- 
tene following. Judging by descriptions of various investigators 
of the zygotene in different animal groups, the amphitene of the 
amphibian germ-cell cycle is a prolonged transition stage between 
leptotene and pachytene. In typical amphitene nuclei one finds 
the nucleus marked off into two more or less distinct portions by 
the type of chromatin thread present. At the proximal pole of 
the nucleus, i.e., that side nearest the centrosome and sphere, 
the dehcate leptotene filaments have disappeared, and one finds 
only the thickened pachytene threads ; conversely, at the distal 
pole of the nucleus, i.e., the pole opposite the sphere, the leptotene 
condition persists. By focusing through a single cell, it is possible 
to bring into view now a leptotene, now a pachytene condition 
(figs. 11 to 13, 36 to 38). The explanation of this apparently 
anomalous condition is simply that the thick pachytene threads 
of the proximal pole of the amphitene nucleus represent the longi- 
tudinal fusion (parasynapsis) of two originally distinct leptotene 
