466 



SCIENCE 



[N. S. Vol. XXXI. No. 795 



lieved had been confined beyond the possibility of 

 impregnation, from the evidence presented it 

 would appear that ovulation in this animal, as 

 well as in the rabbit (Heape') and ferret (Mar- 

 shall*), is strictly dependent upon pairing. 

 Early Maturation Phenomena in the Primary 



Oocyte of Sahellaria vulgaris (Verrill) : H. E. 



Jordan, University of Virginia. (Presented by 



title.) 



Only ovarian and free ccelomic eggs have been 

 studied. The material was collected at Cold 

 Spring Harbor, L. I. The youngest oocyte, almost 

 wholly nucleus, has a diameter of 4 microns. The 

 diameter of the full-grown egg varies from 50 

 to 60 microns. Maturation proceeds to the meta- 

 phase of the first polar spindle in the ovary, after 

 which a pause ensues until fertilization. The 

 youngest oocytes are in synizesis. The intensely 

 chromatic spireme is distinctly polarized. The 

 spireme segments into a large number of V-shaped 

 chromosomes. The shape and manner of forma- 

 tion of the latter suggests telosynapsis. 



The chromosomes persist in various shapes 

 through the entire growth period. The chromo- 

 somes, as arranged on the spindle, are very small 

 and slender. As many as forty have been counted 

 in three consecutive sections, but this may repre- 

 sent a second count of several. Occasionally, the 

 chromosomes are massed close to the nucleolus 

 before their entrance into the spindle. The spatial 

 relationship between the chromosomes and the 

 nucleolus appears less intimate than in several 

 forms studied, e. g., Asterias and Cumingia. 



Both nucleolus and centrosomes disappear at 

 metaphase. The cytoreticulum is coarse and its 

 meshes are filled with spheric yolk granules. The 

 astral rays are clearly continuous with the cyto- 

 reticulum. The evidence here favors a spongio- 

 plastic origin of the amphiaster. 

 The Relation of 'Nucleoli to Chromosomes in the 

 Egg of Oriirella sanguvneolenta (Lutken) : H. 

 E. Jordan, University of Virginia. (Presented 

 by title.) 



The material for this study was collected at 

 South Harpswell, Me. The full-grown ovarian 

 egg is very large. It has an alveolar cytoplasm, 

 and its large eccentric nucleus (diameter 300 

 microns) contains very numerous chromatic nu- 



' " Ovulation and Degeneration of Ova in Rab- 

 bits," Proc. Boy. Soc. Lond., Vol. 76B, 1905. 



* " The (Estrous Cycle in the Common Ferret," 

 Quart. Jour. Mio. Soi., Vol. 48, 1904-05. 



cleoli of graded sizes. Occasionally it may also 

 contain an additional very large nucleolus, the 

 remains of the originally single nucleolus. Scat- 

 tered among the nucleoli, and frequently in inti- 

 mate contact with them, are a number of beaded 

 chromatic threads of varying length, the chromo- 

 somes. The nuclear appearance suggests an am- 

 phibian egg. 



The single nucleolus of the earliest stage gives 

 origin to secondary nucleoli, apparently by a 

 process of extrusion. These in turn produce still 

 smaller nucleoli by a similar process. The final 

 products of nucleolar budding are approximately- 

 equal in size to the granules of the chromosomes. 

 The evidence indicates that the chromosomes are 

 formed of the final products of nucleolar disper- 

 sion. The chromosomes arise from the original 

 nucleolus or its products, at least to the extent 

 that their chromatin content is supplied by them. 



An interesting generic diflference in the manner 

 of the formation of the nucleoli obtains between 

 Echinaster and Cribrella. In the former the 

 single nucleolus fragments into secondary forma- 

 tions ; in the latter the nucleolus extrudes second- 

 ary nucleoli. In the former again, the products 

 are usually four-lobed; in the latter spheric. In 

 an earlier study of Echinaster I was inclined to- 

 interpret these quadripartite bodies as chromo- 

 somes or possibly their constituent elements. In 

 the light of facts derived from a study of Gri- 

 irella, it seems more probable that the several 

 beaded chromatic threads found in Echinaster are 

 also there the chromosomes. This, however, does 

 not invalidate the conclusion that in the last 

 analysis the chromosomes arise from the nucle- 

 olus. The four-lobed bodies more probably repre- 

 sent a peculiar stage in the process of nucleolar 

 budding preparatory to chromosome formation as 

 in Cribrella. 



Dimegaly of the Sperm Cells of Eusohistus : T. 

 H. Montgomery, Jr., University of Pennsyl- 

 vania. 

 Experiments on the Effect of Conjugation on the 

 Life History in Paramecium: H. S. Jennings,. 

 Johns Hopldns University. 



Pairs that were beginning conjugation were- 

 isolated, in some cases separating the individuals 

 before conjugation was consummated, in others 

 allowing conjugation to occur. Both sets were- 

 then kept under identical conditions, and their 

 reproductive powers and vitality observed. Com- 

 parison of about two hundred of those that had 

 been allowed to conjugate and of those that ha(S 



