Miscellaneous. 321 



" Illustrations Conchyliologiques, ou Descriptions et Figures de toutes 

 les Coquilles connues." After Kiener's death, this work was continued 

 by M. Chenu, who succeeded him, and it has reached its 84th Part; 

 but I fear there is very little hope now of its being continued 

 further. 



M. Chenu (from the same collection, and I believe by the liberal 

 assistance of its possessor) brought out his most useful ' Manuel de 

 Couchyliologie et de Paleontologie ' — " Conchy liologie " in two large 

 volumes, illustrated with nearly 5000 woodcut figures, which is cer- 

 tainly the cheapest work on science ever pubUshed. 



M. Delessert has certainly done all in his power to illustrate the 

 conchological labours of Lamarck and to forward the science. 



0)1 the Constitution and Development of the Ovarian Egg of the 

 Sacculinae. By J. Gekbe. 



In the ovule of a considerable number of species belonging to 

 various classes of animals, there is, besides the vesicle known to 

 physiologists as the germinal vesicle or JPurJcinjean vesicle, a second 

 vesicle, generally of smaller size, which occupies a position more or 

 less approximate to the former, Wittich, Siebold, and V. Cams 

 have indicated it in the ovules of Aranea domestica ; Balbiani has 

 discovered it in those of the Myriopoda, of the Crustacea of the genus 

 Oniscus, of frogs, of a considerable number of spiders,ifec. ; and,finally, 

 Coste figured it as early as 1847 in the primitive ovule of the bird, 

 immediately above the vesicle which forms the centre of the cica- 

 tricula. 



What is the function of this second vesicle ? Are we to regard it, 

 with Balbiani, as the true formative centre of the germ ? or is it not 

 destined to fulfil some other function ? 



This question may be completely solved by the study of the ovule 

 of those singular parasites the >Sa4:cidin<^ (Sacculina, Cavolini,=Pe/- 

 togaster, Eathke), which are found adhering to the tail in certain 

 Crustacea, especially Cancer mcBnas. 



In these parasites the reproductive organ, which alone forms five- 

 sixths of the mass of the animal, contains ovules of all ages, the 

 various evolutionary phases of which may be traced from their origin 

 to maturity. Taken from about the central part of the organ, these 

 ovules, which are only from 0-06 to 0-08 millim. in diameter, present 

 a form so different from that generally exhibited by those of other 

 animals, that it would be difficult to recognize their true character, 

 if we did not see them pass from this to a more advanced stage, which 

 leaves no doubt on the subject. They are then formed: — 1, of two 

 independent, transparent vesicles, of nearly equal volume, and touch- 

 ing each other almost by a single point of their circumference ; 

 2, of a general envelope (vitelline membrane), which is very delicate 

 and constricted about the point where the two vesicles are in appo- 

 sition ; 3, of a small quantity of colourless substance, excessively 

 finely granulated, which separates the two vesicles from the enve - 

 loping membrane. The ovule, instead of being globular, is there- 



Ann.& May. N. Hist. Ser. 4. Vol.m. 24 



