LEUCKART, ON MICUOPYLE. 289 



even with many such openings — with micropyles extending 

 over larger and smaller portions of the whole vitelline 

 membrane. 



These latter instances render it very probable that the 

 peculiar system of orifices and canals which, according to the 

 observations of J, Miiller (' Monatsb. der Berlin. Akad.' 

 1854, p. 164) and Remak (Muller, « Arch.' 1854, p. 252), 

 pervades the chorion of our indigenous osseous fishes, also 

 belongs to the category of micropyle apparatus, and is sub- 

 servient to the act of impregnation. It is true that this 

 explanation of the import of these passages can only be satis- 

 factorily established by means of the microscope ; but this 

 will perhaps remain a problem of difficult solution, as it can 

 scarcely be supposed that the spermatic filaments penetrate 

 through the solid chorion and make no use of the openings. 

 It is far more doubtful with respect to the radiating streaks in 

 the zona pellucida of the mammalian ovum, which are com- 

 pared by Remak with these orifices in the fish's egg. It does 

 not even appear that these markings can properly be esteemed 

 as the optical expression of canals, seeing that neither lumina 

 nor orifices can be perceived in them. This much, however, 

 seems to have been made out, that the markings depend upon 

 a definite structural condition ; it must even be allowed that 

 the same conditions of structure may possibly indicate the 

 way followed by the spermatic filaments in their passage into 

 the ovum, and by which they penetrate the zona pellucida. 

 Even as canals, these passages would still require dilatation 

 in order to allow of the transit of the spermatic filaments, 

 which are found in the interior with their heads and tails. 

 In adverting to these micropyle-like markings, J. Miiller 

 takes occasion to notice the radiating lines of the chorion in 

 the ova of Tania. Leuckart has examined this in various 

 species (T. serrata, T. ccenurus, &c.), and, from the optical 

 conditions presented, is satisfied that the markings depend 

 upon closely-placed perpendicular canals (1-2000"). But, 

 whether these canals penetrate the chorion completely, he 

 leaves undecided. And it must, of course, remain equally 

 doubtful whether they fulfil the function of a micropyle. At 

 the same time, he says that he does not believe such to be 

 their nature ; in the first place, because these canals in other 

 cestoid worms {Ligula, Tetrarhynchus), as well as in Tania 

 cucvmerina, &c., are wanting, and also, for the reason that 

 since, according to the anatomical conformation of the sexual 

 organs in these animals, impregnation takes place before the 

 formation of the chorion, any introduction by means of a 

 micropyle can scarcely be required. 



