1907] GATES—POLLEN DEVELOPMENT AND MUTATION 107 
reduction mitoses, and perhaps from irregularities in the distribution 
of chromosomes. The results of the paper mentioned above would 
also appear to show that a relation exists between chromosome 
morphology and the morphology of the pollen grains. 
The origin and early stages of some of the bodies classed as 
‘idiochromosomes” by WILSON (36) are similar to those I have found 
in Oenothera. In Lygaeus turcicus, one of the Hemiptera, a large and 
a small idiochromosome are found in the prophase, the large one first 
appearing about the time of synapsis. Slightly later it is seen as a 
more deeply staining longitudinally split thread among the chromo- 
somes, which are also thread-like bodies at this time. During this 
period a smaller, somewhat elongated idiochromosome is also present. 
The larger idiochromosome condenses to a globular shape and is 
for a time attached to the plasmosome, but retains a central cavity, 
which represents the original longitudinal split. This makes its 
appearance quite similar to those described in Oenothera. The 
later history of the idiochromosomes in Lygaeus and other Hemiptera 
however, is quite different from those of Oenothera, and need not be 
taken up here. Small chromosomes, which possibly correspond with 
Witson’s m-chromosomes, are also occasionally found in Oenothera 
(figs. 26, 27). 
Miss STEVENS (28) has described chromatic bodies in the insects 
which correspond with the heterochromosomes of Oenothera in 
parts of their history. In Stenopelmatus, the ‘“‘sand-cricket,” a 
chromatic “element x” appears in synapsis in the spermatocytes 
attached to an end of the spirem. It passes undivided into one of 
the spermatocytes of the second order and there degenerates during 
the resting stage between the maturation mitoses. Miss STEVENS 
believes this to be rejected chromatin, analogous to that observed 
in the ovogenesis of many forms. In the animal Sagitta, which is 
hermaphrodite, Miss STEVENS (2'7) found in spermatogenesis bodies 
which resemble the heterochromosomes of Oenothera in some respects. 
This “element «” appears in the spermatogonial divisions, where it 
divides before each mitosis. It also divides in the prophase of the 
first maturation division, and when the chromosomes are on the 
equatorial plate in metaphase these bodies are found in various 
