56 J. F. MtCLENDON. 



For cell lineage, whole eggs had to be used, and it was 

 exceedingly difficult to get them out of the egg tube. The best 

 way is to separate the eggs by cutting the tube between them 

 with a sharp "spear head " dissecting needle under the micro- 

 scope, which increases in difficulty in proportion to the flattening 

 of the eggs. When the eggs are separated the polar bodies are 

 lost and other means of orientation are necessary. In stages 

 before the origin of the primary germ cell it was necessary to 

 lay the eggs on the slide with a determined pole uppermost. 

 The eggs, except when abnormally placed, have the vegetal pole 

 turned toward the mother, and by placing the mother and 

 attached egg strings in cedar oil on a slide under a Zeiss binocu- 

 lar dissecting microscope, it was possible to lay the eggs with 

 vegetal pole up as they were separated, place a cover glass over 

 them to prevent turning, and run balsam under from one side. 



Schimkewitz ('96, '99) concluded that pressure was an im- 

 portant factor in determining the form of the cleavage of para- 

 sitic copepods. 



Pedaschenko ('93, '97, '98) worked for a number of years on 

 the embryology of Lerncsa branchialis and traced the cell lineage 

 to the 16 cell stage, but was mistaken in the orientation, thinking 

 the first protoplasmic cell to be formed at the animal pole and 

 not distinguishing between the two flat surfaces (dorsal and ven- 

 tral) of the egg in early stages. He found the germ cells to 

 arise from four cells at the edge of the blastopore and consid- 

 ered two of these to be male and two female. The identity of 

 two of these cells was lost (incorporated in the other two) and 

 the remaining two gave rise to the sex glands. If such were the 

 case, it seems to me that we should expect frequent occurrence 

 of bilateral androgyny (hermaphroditism). The close relation of 

 Lernaea to the forms I studied has made Pedaschenko's work of 

 great service as a hand-book. 



Grobben ('79) had long before found the germ cells to arise 

 from four cells of the anterior lip of blastopore of the phyllopod, 

 Moina. 



C. B. Wilson ('05) includes in his excellent monograph of the 

 Caligidae, a description of the general embryology of these para- 

 sitic copepods. 



