140 



MISCELLA>'EOUS. 



Upon the Mode of Formation of the Egrj and the Einhryonic Develop- 

 ment of the Sacculinae. By M. E. van Bexedex. 



Ix a note inserted in the ' Comptos llendus ' of the month of 

 February last (February 22, IJ^OO), M. Gerbe has given the results 

 of his researches upon the constitution and development of the 

 ovarian egg of the >Saa-idin(.T. According to this avthor, the ovules 

 are formed at their tirst appearance of two transparent cells closely 

 applied to each other, each provided vrith a vesicular nucleus and a 

 common membrane (vitelline membrane). One of these cells in- 

 creases considerably, there are developed in it a large quantity of 

 refractive globules ; whilst the other remains small and only acquires 

 a few tine globules ; and when the egg is mature, the lai-ge cell, in 

 which the elements of the yolk are develojicd, has attained such a 

 predominance that the other lobe, of which the develo])ment has 

 remained in some sort stationaiy, only represents a small, scarcely 

 perceptible eminence upon one of the poles of the ovule. M. CJerbe 

 regards the large cell as giving origin to the vitellus, and com- 

 pares it to the yolk of the egg of birds ; whilst the little cell, in his 

 opinion, represents the germ or cicatricula. Moreover M. Gcrbe 

 thinks he finds in the development of the ovum of the Sacculina; the 

 explanation of the physiological part perfonncd in the egg by that 

 body which Ton "Wittich, Yon Siebold, and Y. Cams have described 

 in the cg^ of several spiders, by the side of the vesicle of Piirkinje, 

 and which M. Balbiani has observed in certain Myriopods. One of 

 the two cell-nuclei of the primitive bilobed ovule of the Sacculinae 

 would be the nucleus of the formative cell of the vitellus and the 

 homologue of the vitelline nucleus of the egg of the spiders ; the 

 other would be the germinative nucleus or the nucleus of the germ- 

 cell, the homologue of the germinal vesicle of the egg of the spiders 

 and 3Iyriopods. 



The observations which I have made upon the development of the 

 ovanan egg of the t^acculinft agree, in certain points, with those of 

 the learned embryogenist of the College of France ; but the inter- 

 pretation which I have given to the facts is essentially different, 

 which is due to the circumstance that, upon some points, I am not 

 able to confirm the investigations of M. Gerbe, and that some im- 

 portant facts have escaped his attention. 



The ovules are not, at their first appearance, formed of two cells 

 closely applied to each other ; they consist, at first, of a single cell, 

 formed of a perfectly transparent viscous matter (protoplasm ) hold- 

 ing in suspension some globules which strongly refract the light, 

 and of a vesicular nucleus, with very delicate outlines, measuring 

 about half the diameter of the cell and provided with a single very 

 refractive nucleolus. The diameter of this cell is about 006 millim. 

 Along with these cells are seen others, which present an elongated 

 form and are provided with two nuclei, without, however, mani- 

 festing any tendency to the division of their bodies. Others, on the 



