46 SUiMMARY OF CURRENT RESEARGEIES RELATING TO 



is formed for each brood, and some species have three broods in a year. 

 A young form must live for at least a winter before it is mature. The 

 two pairs of accessory hepatic tubes have in terrestrial Isopods a primary 

 function as stores for the yolk left over from the embryonic period. An 

 account is siven of the development -of monostigmatic and polystigmatic 

 tracheal systems. AVe cannot do more than indicate the scope of a 

 paper rich in detailed results. J. A. T. 



Studies in Asellidae. — B. G. Racovitza (Arch. Zool. Exper., 1920, 

 58, Notes et Revue, 79-115, figs. 52-84). A study of the North 

 American species Asellns rommnnis, which shows a strange combination 

 of highly specialized and very primitive characters. Likewise a study 

 of the structure and development of the first and second pleopods of 

 Asellidte, which have come into the service of reproduction. The first 

 pleopod of the male is reduced to two undivided joints, a sympodite 

 and an exopodite. It is absent in the female. The second pleopod of 

 the male consists of an undivided sympodite, a slightly modified 

 biarticulate exopodite, and a biarticulate or undivided endopodite trans- 

 formed into a copulatory organ. In the female it is an unjointed 

 fusion of sympodite and exopodite. J. A. T. 



Early Development of Rock-barnacle. — H. C. Delsmax {Tijdschn 

 Nederland.Dierlc. Ver., 1917, 15, -119-520, 15 pis., 8 figs.). The ovum 

 of Balanus halanoides is among the largest of Cirripede ova ; it is the 

 richest in yolk ; its segmentation is mainly unequal. From the fertilized 

 ovum four yolkless micromeres are constricted off, marking the separa- 

 tion of ectoderm and endoderm. Then follows the division of the yolk- 

 containing macromere into two approximately equal cells. At the sixth 

 cleavage each of the two yolk-cells gives off a small yolkless cell, a meso- 

 blast. Further divisions of the yolk-cells lead to the primordium of the 

 mid-gut. The four micromeres form a cap growing round the yolk-cell 

 or yolk-cells. Their divisions are equal. Gastrulation is epibolic, the 

 micromeres growing round the endoderm. The blastopore is dia- 

 metrically opposite the animal pole. At the completion of the epibole 

 there are two yolk-cells. Most of the mesoblast arises from ecto- 

 dermic micromeres at the margin of the blastopore ; the entomesoblast 

 has been already referred to. A remarkable feature is the origin of the 

 proctodeum from the distal end of the stomodsal invagination. The 

 number of chromosomes in the somatic cells is thirty-two. J. A. T. 



Appendage of Sex-intergrade of Daphnia longispina. — A. M. 



Banta anil Mary Gover {Proc. Amer. Soc. Zool. in Anat. Record, 1920, 

 17, 348-9). Every detail of the first leg which is subject to .sexual 

 modification is also subject to intermediate development. Any portion 

 may show- any condition from a slight departure from the type of the 

 normal female to an approximation to the typical male. The different 

 portions of the same individual appendage may show a range from 

 fully female to moderately male in character, or from an intermediate 

 condition to a fully male condition. There is, however, a certain amount 

 of correlation between the degree of maleness and f emaleness manifest in 

 the different portions of the same appendage. J. A. T. 



