. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. [102]. OVUM. tents of the vesicle, the more immediately germinal part of the egg is formed from the mixture of the two. However this may be, it seems not improbable, from the observations now referred to, that the spermatozoa are conveyed directly to the germinal part of the egg by the funnel of the micropyle. I shall afterwards have to state the more numerous instances in which, following its first discovery by J. Mtiller in the Holo- thuria, a micropyle has been detected in the ova of Invertebrate animals; and I may at
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. [102]. OVUM. tents of the vesicle, the more immediately germinal part of the egg is formed from the mixture of the two. However this may be, it seems not improbable, from the observations now referred to, that the spermatozoa are conveyed directly to the germinal part of the egg by the funnel of the micropyle. I shall afterwards have to state the more numerous instances in which, following its first discovery by J. Mtiller in the Holo- thuria, a micropyle has been detected in the ova of Invertebrate animals; and I may at- tempt to show the great importance of this aperture in connection with fecundation in ova with thick external coverings to which the spermatic substance does not gain access till the later periods of their formation. The ac- companying figures of the micropyle in the Stickleback will give a sufficiently clear view of this remarkable structure. At present it may be permitted to remark that, if we consider the size of this aperture, and the ease with which it may be found in the ova of fishes by an observer whose at- tention has been called to its existence, to- gether with the fact of its having been so long overlooked previously, there is much ground for caution as to negative statements as to the existence of a similar aperture in the ova of other animals. I have already made al- lusion to this subject in the previous sections, in which I have stated that Dr. Ransom has expressed to me his firm conviction, founded on observations, that the micropyle exists also in the ova of Batrachia. At the same time it is quite probable that such an aperture may only exist or be required for the admission of the spermatozoa when fecundation is of late oc- currence, and when the covering membrane of the ovum is so dense as to resist the pene- tration of the spermatozoa through its solid substance. It is right also to mention that the exist- ence of this aperture, or rather the funnel lead
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