386 



SCIENCE. 



[N. S. Vol. XXI. No. 5.32. 



ous specimens illustrating the mode of life 

 and especially the structure of the mouth- 

 parts were exhibited. 



The Color-Pattern of Nancmijs guttata 

 Schneider (a preliminary report) : Rob- 

 ert M. Yerkes, Harvard University. 



1. The young of this species of tortoise 

 usually have a single yellow spot on each 

 plate of the carapace, except the marginals. 

 AVith age the number of spots increases, 

 they appear on the marginal plates also, 

 and their arrangement becomes irregular. 



2. The epidermal layer is transparent 

 immediately over the mass of yellow pig- 

 ment in the outer bony layer, hence, 

 window-like regions in the outer portion of 

 the shell. 



3. Although the females are slightly 

 smaller than the males they usually have 

 about 15 per cent, more spots on the cara- 

 pace. The average number for the males 

 is 60, for the females 69. This would seem 

 to indicate that the brightly colored spots 

 serve as both sex and species marks. Prob- 

 ably they serve to render the females con- 

 spicuous. 



4. Statistics indicate a greater number 

 of spots on the left side of the carapace 

 than on the right in both males and fe- 

 males. It is possible that this is to be cor- 

 related with right-handedness and right- 

 eyedness. 



Chromosome Vesicles in the Maturation of 

 Nudibranchs: W. M. Smallwood, Syra- 

 cuse University. 



Between the anaphase of the first matu- 

 ration and the prophase of the second the 

 chromosomes pass through some important 

 changes. The first indication of the pres- 

 ence of vesicles is noted at about the time 

 that the young amphiaster of the second 

 maturation figure is forming and moving 

 into a radial position. At this time a dis- 



tinct membrane appears around each chro- 

 mosome, which lies so close to the chromo- 

 some as to be overlooked in some instances. 

 It frequently happens that one chromo- 

 some vesicle contains two or more chromo- 

 somes, in which case the chromosomes are 

 united by narrow strands of chromatin. 



The chromosomes do not always pass into 

 vesicles, but go through the well-known 

 changes as described for other molluscs, 

 annelids, etc. 



During the prophase of the second matu- 

 ration the solid chromosomes enclosed in 

 vesicles may lose their reaction to basic 

 stains almost entirely, with the result that 

 each vesicle represents in miniature a nu- 

 cleus having chromatic granules, linin 

 threads and an achromatic substance. 

 After this condition the granule, or gran- 

 ules, within the chromosome vesicle in- 

 creases in size until it has the normal ap- 

 pearance of a chromosome lying in the 

 cytoplasm. It is an open question as to 

 the fate of the surrounding vesicle. 



The fibers constituting the second matu- 

 ration spindle are formed in part of the 

 eggs from the cytoplasm after the spindle 

 has taken a radial position and the centro- 

 somes are fully differentiated into centriole 

 and centroplasm. 



The chromosomes which pass into the 

 first and second polar cells may each have 

 a separate vesicle or all of the chromosomes 

 may pass into one vesicle. All combina- 

 tions between these two extremes occur. 



These and similar results on Haminea 

 suggest that the chromatin passes through 

 a liquid state during maturation, at which 

 time there may be a complete chemical re- 

 arrangement of the molecules in the chro- 

 mosome, which, if it were true, would inter- 

 fere to some extent with the theory of the 

 qualitative division of the chromosomes. 



The complete paper will appear in the 

 Morphologisches Jahrlmcli, Bd. XXXIII. 



