971 



shows that it is of the chondriforra type, being developed in a thick 

 leathery periosteum of fibro-cartilage, and which appears to be con- 

 tinuous with the true cartilage wherever the two come into contact. 



It is not possible to give any definite idea of the detailed observa- 

 tions contained in a memoir of which so large a portion is devoted 

 to minute investigation. The inferences which the author deduces 

 from his facts are given in connexion with each of the several topics 

 discussed ; and in the concluding portion of the memoir he points 

 out the bearing which they have upon some general questions in 

 physiology. A close resemblance is shown to exist between the pro- 

 cesses of calcification, as carried on in the fibrous tissues of fish-scales, 

 in cartilages and in fibro-cartilages, in all of which the phtenomena 

 closely correspond ; and the author thinks that the bones and teeth 

 of mammals, in which the process is far less obvious than in these 

 ichthyal structures, may be calcified in a similar way. 



The important bearing of the membraniform kosmine structures 

 (which closely resemble the different varieties of dentine) upon the 

 generally received hypothesis respecting the growth of teeth is also 

 discussed ; and the author thinks there are such sufi^icient reasons 

 for doubting the correctness of that hypothesis, as to render a review 

 of the evidence upon which it is based very desirable. 



The peculiar modifications which the homologues of the Haver- 

 sian canals of anthropotomists present amongst different groups of 

 fishes are pointed out, as well as the very near affinity which exists 

 between bone, dentine, ganoin, kosmine, enamel ; and the proba- 

 bility of a closer relationship between cartilage, fibro-cartilage and 

 fibrous periosteum, is also suggested as a subject deserving further 

 investigation. The field opened out to the physiologist and the 

 microscopist in the department of ichthyology is almost boundless, 

 being comparatively unexplored, whilst it promises a rich harvest to 

 those who labour in it. 



7. "On the Impregnation of the Ovum in the Amphibia." By 

 George Newport, F.R.S., F.L.S. &c. 



The author states that this communication to the Royal Society 

 is part of a series of investigations on development, on which he has 

 been for some years engaged, and which was commenced in a paper 

 on that of the Myriapoda, published in 1841, in the Philosophical 

 Transactions. The plan followed in these investigations has been 

 to combine observations on the natural history of the animals with 

 others on the conditions which affect their development, as the best 

 mode of arriving at correct conclusions. The history of the dis- 

 covery of what can now be proved to be the direct agent of impreg- 

 nation, the spermatozoon, is then traced; and it is shown, that 

 although within the last few years an opinion has been gaining 

 ground that the spermatozoon, and not the liquor seminis, as for- 

 merly supposed, is the means of impregnation, no acknowledged 

 proof has hitherto been given of the correctness of this opinion, and 

 no refutation afforded to the theory that the liquo?' sembiis is the 

 part of the seminal fluid immediately concerned. The question of 



