634 J. T. PATTERSON 



segmentation of the egg. Furthermore, he points out that the 

 early blastomeres of the egg of Crisia are separated from each 

 other by follicle-tissue, and that they are surrounded by a rich 

 nutritive material, which is obtained through the protoplasmic 

 strands connecting the several units of the colony with the ovi- 

 cell. He believes that the production of numerous larvae from 

 the primary embryo in Crisia is a process comparable to arti- 

 ficial blastotomy in Echinus eggs, as shown by the experiments of 

 Driesch ('92). His general conclusion is clearly stated in the 

 closing paragraph of his paper. He says : 



TJie cases already quoted may be taken as showing that some of the 

 abnormalities in the development of Crisia may be due to the nutritive 

 conditions in which the development takes place. Just as the presence 

 of food-yolk within the egg modifies the character of the segmentation 

 and the formation of the layers, so the presence of copious stores of nu- 

 trient material in the maternal tissues outside the egg may also effect the 

 early developmental processes. Thus the large number of relatively 

 large larvae which develop from the minute egg of a Crisia could not be 

 produced if the egg were not supplied with nutriment from outside it- 

 self. While some of the irregularity in the segmentation of the egg may 

 be due to this cause, the extreme independence of the blastomeres at an 

 early stage may be connected with the acquirement by the embryo of a 

 habit of forming buds in the embryonic condition. 10 



Marchal ('04) has expressed somewhat similar views, as may 

 be gathered from the following quotation. 11 



As to the determining cause of the division of the germ, Marchal 

 thinks that it is from the sudden surrounding with more dilute liquids in 

 the interior of the nourishing mass and in a concomitant modification of 

 the osmotic exchanges in the interior of the cellules. One sees, in 

 fact, with Encyrtus that polyembryony reaches its greatest intensity at 

 the moment when the larvae of the Hyponomeuta commences to feed 

 (in the early days of April), and for the Polygnotus at the period when 

 the young larva of the Hessian fly engorges itself with sap. Now, the 

 production of the rapid changes bringing about osmotic pressure con- 

 stitutes precisely the procedure employed to bring about the separation 

 of the blastomeres and their evolution into several distinct individuals, 

 as has been shown by the experiments already mentioned of Loeb and 

 Bataillon. 



10 Loc. cit., p. 236. 



11 From Howard's ('06, p. 816) clear translation of Bugnion's ('06) review of 

 Marchel's ('04) paper. 



