142 Miscellaneous. 



polar cell. When the egg has arrived at maturity, it presents a 

 regular ellipsoidal form, and at one of its poles the polar cell is 

 always found, retaining its hemispherical form and its original 

 transparency and dimensions. This cell is outside the vitelline 

 membrane, of which we can follow the perfectly regular dark out- 

 line between the vitellus and the polar cell on a level with the sur- 

 face of attachment ; the vitelline membrane, however, is slightly 

 depressed, and perhaps it is wanting, at the centre of this surface. 



Along with those mature eggs which bear near their poles a 

 transparent coU, are others in which it is not possible to distinguish 

 any polar cell, but which still present, at one part of their surface, a 

 depression corresponding to the old surface of attachment ; the ex- 

 truded eggs never show the least trace of the polar cell, or anything 

 which resembles a cicatricula. Considering this fact in conjunction 

 with that of the existence in the ovary, a little time after oviposi- 

 tion, of isolated cells, which I have called mother cells, and which 

 present all the characters of the polar cells of the mature eggs, we 

 see that the j^oJar cells of the mature eggs are not a constituent part 

 of the egg, coniparahle to the cicatricula of the egg of birds ; these cells 

 separate from the surface of the mature eggs, remain in the interior 

 of the ovarg, and increase in number by division to give birth to two 

 daughter cells, ivhich remain attached to each other, and of tvJiich one 

 j)rodi(ces in its turn an egg. The body which M. Gcrbe has re- 

 garded as representing a vitelline cell, destined to form the nutritive 

 elements of the vitellus, is in reality the entire egg; its nucleus re- 

 presents the germinal vesicle ; and its contents consist of a homo- 

 geneous protoplasmic liquid, holding in suspension some refractive 

 globules (nutritive elements of the vitellus). 



These observations suffice, it appears to me, to justify the con- 

 clusion that I draw from them ; but I find in the analogies which 

 the development of the eggs of the Sacculince present to those of a 

 great number of other Crustacea, and in the development of the 

 embryo of the Saccidinre, the complete demonstration of the conclu- 

 sion which has just been formulated. 



In a great number of parasitic Copepoda {Ckdigus, Clavella, Ler- 

 nanthropus, Conger icola) the ovary presents the form of an oval sac 

 (germiyene), of which the anterior extremity is prolonged into a 

 tube {vitellogene) ; the latter gradually widens and opens exteriorly, 

 after having formed in the interior of the body a certain number 

 of convolutions. The germigene is filled by a very slender trans- 

 parent band, twisted and coiled upon itself, which at the entrance 

 of the gland is produced into the tube which represents the vitel- 

 logene. This cord is really formed of an immense number of small 

 perfectly transparent protoplasmic cells provided with a very small 

 nucleus. They are flattened, and resemble little disks piled together. 

 In the vitellogene each of these little cells increases in size, and 

 becomes filled with refractive elements, to become an e^g, at the 

 same time that their nucleus becomes the germinal vesicle. The 

 eggs retain this flattened discoidal form, and they are accumulated 

 in the vitellogene like coins. In some other Lernseidaj (Anchorella, 



