GERM CELLS OF ANURANS 293 
11. The sexual cycles of the larval bullfrog are tentatively 
interpreted, in lieu of a more satisfactory hypothesis, as recapitu- 
lations of the germ-cell cycle to past phylogenetic sexual condi- 
tions when the vertebrates ripened their sex products at an earlier 
developmental stage than at present, 
12. An analogous precocity of the maturation cycle probably 
exists in all of the vertebrates, Amniota as well as Anamnia. 
Evidence for this hypothesis is presented in detail. 
B. The chromosomes and larval sexual cycles 
1. The diploid number of chromosomes in the male larva is 
twenty-eight. The elements are J- - and V-shaped and curved 
rods. Portions of certain chromosomes do not take the stain 
under any circumstances and may give the appearance of frag- 
menting into two or more parts. Such appearances of fragmenta- 
tion are illusory. 
2. Spindle-fiber attachment is non-terminal. 
3. The chromosomes exist in definite pairs according to size and 
shape, i.e., there are fourteen pairs of homologues. 
4. The homologues of any pair are not invariably found side 
by side within the nucleus, though in general they are near 
together. 
5. The size and shape relations of the chromosomes are per- 
fectly definite throughout all cell generations, and this is probably 
true not only for the individual, but for the larvae of the species 
a,s a whole. 
6. As an illustration of the statement just made (number 5), 
see chromosome pair marked A in figure 6. These chromosomes 
are peculiar in that the knob-like end-piece is separated from the 
main body of the chromosome by a clear, non-stainable area. 
This peculiarity is probably constant in the cells of the larvae, 
and has been observed in the spermatogonia of twenty-nine indi- 
viduals of various ages and stages of development. 
7. The resting nucleus of the Anuran germ cell is a polymorphic, 
much-lobulated structure, made up entirely of chromosome vesicles 
which are incompletely fused, and in many cases the vesicles are 
