306 M. E. Claparede on the Theory of the 



Another memoir of Meissner's*, which followed immediately 

 upon the former one, extended the results of his observations to 

 two new classes of animals, namely the Insects and the Crus- 

 tacea. The general result of the facts ascertained by him is, 

 that the spermatozoa which are contained in the receptaculum 

 seminis of the female (in Insects) after copulation, penetrate into 

 the vitellus at the moment when the ova descend in the vagina. 

 Por this purpose, these spermatozoa are obliged to traverse an 

 opening or micropyle, which exists both in the chorion and the 

 vitelline membrane. He enumerates a long series of insects in 

 which he observed the micropyle, and sometimes also the pre- 

 sence of spermatozoa in the interior of the membranes. The 

 chorion of the eggs of Insects, and particularly of the Diptera, 

 is often adorned with very regular geometrical designs, and 

 the micropyle is very easily found, as it generally occupies the 

 centre of an elegant rosette situated at one of the extremities 

 of the egg. It is a curious circumstance, that this micropyle 

 of the eggs of Insects is so easily seen, that it has been described 

 and figured in a great many instances, although its function 

 was never suspected. It was regarded only as an ornament, 

 but not as an opening. Swammerdamm, Rosel, De Geer, 

 Reaumur, Kirby and Spence, Ratzeburg, Sepp, Leon Dufour, 

 Herold, Hartig and others have described and figured the 

 peculiarities of the surface of the eggs of a great many insects, 

 — peculiarities which all appear to be referable to the existence 

 of the micropyle. Moreover the observations of Meissner alone 

 would be sufficient to lead us to suppose the general diffusion of 

 this structure of the egg in the whole class of Insects, since he 

 has ascertained the existence of the micropyle in Diptera {Musca, 

 Tipula, Culex), Coleoptera {Lampyris, E later, Telephorus), Lepi- 

 doptera [Adela, Pyralis, Tortrix, Euprepia, Liparis, Pieris), 

 Hymenoptera (Tenthredo, Polistes, Spathiits), and Neuroptera 

 (Adrian, Panorpa). Subsequently Leuckart has published a very 

 remarkable work f on the micropyle of Insects, of which, un- 

 fortunately, only the first hundred pages have as yet (June 1855) 

 appeared. In this he describes the micropyle in the eggs of at 

 kast 200 species, which scarcely leaves room to doubt of the 

 universality of this arrangement in Insects. In a great number 

 of these species he has even directly observed the entrance of 

 the spermatozoa by the micropyle, or at least has found them in 



* Beobachtimgen, &c. No. ii. Zeitschr. fiir wiss. Zool., Sept. 1854. 



t Ueber die Micropyle und den feinen Bau der Schalenhaut bei den 

 Insecteneiern. Miiller's Archiv, 1855. In the ' Handworterbuch der 

 Physiologie/ article Zeugung, Leuckart had already mentioned the micro- 

 pyle as an attenuated part of the chorion, which might probably play some 

 part in fecundation. 



