364 



SCIENCE. 



[N. S. Vol. IX. No. 219i 



A3IERICAN MOEPIIOLOGICAL SOCIETY. 

 II. 

 A Case of Egg Within Egg. F. H. Hereick. 

 A SMALL egg of the fowl, measuring 21 by 

 17 mm., was taken from the yolk of an ap- 

 parently otherwise normal egg. The in- 

 cluded egg possesses a hard shell, shell 

 membrane, albumen and yolk. Various 

 kinds of inclusions belonging to this type 

 have been recorded in the domestic fowl 

 due to fusion of two egg-like bodies in the 

 oviduct of the hen. Small eggs of this 

 character are sometimes laid. They some- 

 times contain albumen and no yolk, and 

 probably never have a blastoderm. The 

 idea has already been expressed, and is ap- 

 parently well founded, that the small egg 

 represents the fragment of a normal egg 

 which was ruptured and threw off a part of 

 its substance at the time of leaving the 

 ovary, such fragments being treated in the 

 oviduct like full-sized ova. 



Secondary Abdominal Pregnancy with Histolysis 



of the Fatus. F. H. Heeeick. 



The case reported occurred in the cat, 

 where rupture of the uterus, leading to in- 

 tra abdominal birth, had resulted in the 

 following conditions : (1) Abnormal de- 

 velopment of peritoneal structures (thick- 

 enings, adhesions, fenestration of the mem- 

 branes, and tag-like outgrowths over them) ; 

 (2) fragmentation of the fcetus, and at- 

 tachment of the parts to the omenta by 

 overgrowth, the result of extensive pro- 

 liferation in the constituent cells of these 

 membranes ; (3) the more or less complete 

 replacement of the soft embryonic tissues 

 by the proliferating cells. 



On the Early Development of Cerehratnlus. W. 



R. CoE. 



The processes concerned in the matura- 

 tion and fertilization of the ovum of C. mar- 

 ginatns agree closely with those which have 

 been described by Kostanecki and Wier- 

 zejski for Physa, and by Child for Arenicola. 



The centrosome arising from the sperm- 

 atozoon divides early. The division of its 

 aster is accompanied with the formation of 

 a delicate central spindle. The sperm- 

 asters eventually degenerate, although their 

 rays often remain even after the cleavage- 

 asters have appeared. Their centrosomes 

 usually become lost to view. Occasionally, 

 however, it can be demonstrated, with a good 

 deal of certainty, that they do not actually 

 end their existence, but retain their identity 

 and become the centers of the cleavage 

 asters. 



The centrospheres of the cleavage asters 

 increase enormously in size. They are not 

 artifacts, for they may be seen in the living 

 egg. The centrosomes are very minute. 

 They divide early, and the asters of the 

 second cleavage begin to form about them 

 quite within the body of the centrosphere, 

 as in the Thalassema. 



The eggs of Micrura coeca and Cerehratnlus 

 leidyi furnish almost ideal examples of the 

 regular spiral type of cleavage. The first 

 two cleavages are almost exactly equal in 

 size. In the third division the upper four 

 cells are slightly larger than the lower four> 

 A very regular blastula results. The marked 

 backward inclination of the enteron is evi- 

 dent from the very beginning of gastrula- 

 tion. 



At the end of the first day the enteron 

 becomes divided into two distinct regions. 

 Pseudopod-like processes of cells grow out 

 to separate the two cavities and almost com- 

 pletely. The posterior blind sack of co- 

 lumnar cells is not definitely cut off from 

 communication with the exterior, however,, 

 and food may enter by a temporary open- 

 ing between the cell-processes. 



Large cells of the larval mesenchyme, 

 which wandered into the segmentation 

 cavity at the beginning of the gastrulation, 

 multiply rapidly and arrange themselves in 

 certain definite positions, as in C. lacteus. 

 Most of them send out branching and 



