l6O CHAS. W. METZ AND JOSE F. XONIDEZ. 



These include, for the most part, the "chromosomal vesicles" 

 of Conklin ('01, '02, etc.), Wenrich (16), Richards (17) and 

 others. A resume of the observations on these structures up to 

 1917 has been given by Richards (/. r.), who cites examples in 

 various organisms from molluscs to vertebrates (fish eggs). There 

 is considerable difference in the structure of the vesicles in differ- 

 ent forms, but at certain stages in several, if not all, of them it 

 consists of a hyaline outer layer surrounding a more or less defi- 

 nite chromatic axis, suggestive of the lobes in Lasiopogon. This 

 is clearly the case in spermatogonial telophases of the Orthoptera 

 and in Fund ill us eggs (cf. Wenrich, Richards). The stages in 

 which such a condition exists (prophases in the case of Fundulus) 

 may be preceded by others in which the chromatic material is 

 scattered through the vesicle, or even largely applied to the sur- 

 face (Crepidula, Conklin '02). In Fundulus eggs and in the 

 Orthoptera the anaphase chromosome swells into a vesicle in 

 which the chromatin appears as a granulated network. This 

 persists through the resting stage and then the network condenses 

 into a chromatic thread or rod, extending more or less axially 

 through the vesicle. 



If we assume that the hyaline portion of the vesicle is more 

 dense or gelatinous than the surrounding cytoplasm, as is sug- 

 gested by the appearance and behavior of the vesicles, then the 

 structure bears a close resemblance to that in Lasiopogon. On 

 this basis we might conceive of the structures in Lasiopogon as 

 arising in a similar fashion i.e., by the swelling of telophase 

 chromosomes into vesicles, with a diffusion or dispersal of the 

 chromatin (as seen in the early growth stages) and then its re- 

 condensation within the vesicle. The term "vesicle" is perhaps 

 inexact in the case of Lasiopogon for no limiting membrane, ex- 

 cept the nuclear membrane, is visible around the hyaline layer. 

 But the periphery of the latter would, on this view, be consid- 

 ered as analogous to the periphery of the vesicle, whether en- 

 veloped in a membrane or not. 



The only other description of a structure similar to these, so 

 far as we know, is that of Lee's "chromosomal sheath. " l In the 

 case of the Orthoptera cited by Lee his sheath evidently corre- 



1 We are indebted to Professor L. W. Sharp for calling our attention to Lee's 

 paper and to de Litardicre's criticism of it mentioned below. 



