288 LEUCKART, ON MICROPYLE. 



through a micropyle in the animal ovum. Meissner's 

 researches noticed above, however, can, Leuckart says, be 

 taken into account in part, so far only as they apply to the 

 insect-ovum. His statements respecting the ovum of Ascaris 

 and its micropyle, Leuckart is unable, as concerns the present 

 question, to regard as decisive, as he always found it impos- 

 sible to convince himself, in general, of the existence of a 

 vitelline membrane (Eihiille), nor, consequently, of a micro- 

 pyle, at the proper stage of development of those ova. Had 

 it even been proved that the conical discs regarded by 

 Meissner as the spermatic corpuscles, and which he states 

 penetrate into the vitellus through a micropyle, were really 

 the fertilizing elements, even in this case he is only prepared 

 to admit this much — that Meissner had shown in the 

 Ascarides the penetration of the spermatic corpuscles into 

 the, as yet, membrmieless vitelline mass. 



Previously to the observations of Meissner and Leuckart, 

 the known number of animals whose ova are furnished with a 

 micropyle apparatus was very small. Among these could be 

 reckoned with certainty only the Holothurioi (Miiller, 

 Leuckart, and Leydig) and Opldothrix fragilis among the 

 Echinoderms (J. Miiller), Sternaspis thalassimoides among the 

 Worms (J. Miiller), Unio, Anodonta (Leuckart, Keber, 

 BischofF, Hessling) and Venus decussata (Leydig) among the 

 Bivalves. All these animals have a simple micropyle, which, 

 according to Leuckart's observations on the Naiadce (Wagner's 

 ' Handw. d. Phys.' Art. Zeugung, p. 801) and Holothurue 

 (BischofTs ' Widerlegung,' p. 39), and which have since, in 

 all essential points, been confirmed on various sides, always 

 appears to be developed as a kind of stigma. 



It might, consequently, almost have been concluded that 

 the micropyle, in general, existed only in those ova which, at 

 an earlier period of development, had been in continuous 

 connexion with the wall of the glandular follicle. The dis- 

 covery of the micropyle of the insect-ovum shows how hasty 

 such a conclusion would have been. We find a micropyle 

 in ova which are at all times free in their glandular follicles ; 

 it is clear, also, that this opening is formed in some other 

 way than by the dissolution of a previous connexion — that it 

 may arise in consequence of resorption. To this may be 

 added, that the micropyle apparatus of the insect-ova, ac- 

 cording to my researches, presents the most remarkable 

 diversities in form and construction — such, in fact, as could 

 liardly have been previously imagined. Besides ova with a 

 simple micropyle, we are now acquainted with numerous 

 instances in wliich they are furnislied with compound, and 



