276 WILBUR WILLIS SWINGLE 
The view of Eisen ('00) that the definitive chromosomes of 
the spermatocyte are derived from the chromoplasts and that 
''chromoplasts guide the formation of the chromosome just as the 
archosomes guide the formation of the spindles," does not seem to 
be entirely substantiated by conditions in the bullfrog tadpoles. 
In this form the chromoplasts appear to have little to do with the 
origin of the definite chromosomes in so far as the chromatin 
material is concerned, for this originates from the preexisting 
chromatin blocks of the last spermatogonia! telophases by a spin- 
ning-out process of the leptotene threads. But it is very likely, 
and my own observations bear this out, that the chromoplasts 
do give up substance to the chromosomes, though just what the 
nature of this substance is the writer is unable to say. It is doubt- 
ful if the chromoplasts are composed of true basi-chromatin. 
In early stages of chromosome formation, such as the prelepto- 
tene and leptotene, the chromoplasts are usually large heavily 
staining bodies, to which are attached several chromatin threads. 
As development of the threads proceed, the chromoplasts become 
smaller and take the stain with less avidity. In still later stages 
they become vacuolated as if being drained of their contents by 
the growing threads. In final stages these bodies disappear. 
5. Significance of the inaturalion cycle in the larvae 
It is possible that the precocious, seasonal ripening of the 
male germ cells of larval bullfrog represents a recapitulation in 
ontogeny of a primitive, phylogenetic sexual cycle of ancestral 
forms, when the Anura were sexually mature and reproduced 
as larvae, much in the same fashion as does the axolotl to-day. 
Few biologists would hesitate nowadays to deny that the latter 
is not merely a neotenous, gigantic, sexually mature larva of the 
urodele Amblystoma tigrinum, in view of the work of Chauvin 
('75) and Dumeril ('65). The question why this animal some- 
times fails to undergo metamorphosis in certain districts does not 
concern us here (Swingle, '19). Besides the axolotl there are 
numerous other instances on record of neotenous, sexually ma- 
ture amphibians that have failed to metamorphose at the proper 
time. So far as the writer is aware, such individuals are confined 
