V. Description of a Mammalian ovum in an early condition of development

The opportunities which present themselves for the acquisition of the ova of Mammalia during the early stages of development, and especially ova of the period during which the formation of the blastodermic layers is proceeding, are so rare that, although the subject has been under special investigation by more than one observer, all the stages of the process of formation have by no means as yet been described; and much remains to be discovered in connexion with this phase of development alone. It seems on this account desirable to publish observations bearing upon this question, although they are limited to two or three or even to a single ovum, since it is by collecting and comparing the results which have been arrived at by different observers that there will be the best chance of coming to a definite conclusion upon a subject which involves the knowledge of every progressive stage. I have been induced by these considerations to furnish a short description of an early developing ovum (of the cat) which came into my hands now fully two years ago, but which I had continually deferred the account of in the hope of obtaining specimens a little more in advance with which to compare that which I already had. This expectation having, however, hitherto been disappointed, I think it better to communicate the description without further delay, as it may at least serve for comparison with the statements of other observers.