AND THOSE OF CERTAIN OTHER MAMMALIA. 109 



Why within the limits of so well-defined a class such wide 

 variety should exist in the means by which is carried on and out 

 that intra-uterine life which every member of the class lives alike, 

 it is difficult for us to understand ; but that such variety does exist 

 there is no doubt. 



Differences, however, in structural arrangements which do exist, 

 without our being able to see why they should exist, possess 

 a morphological value which rises in direct proportion with their 

 physiological obscurity. 



BIBLIOGRAPHY. 



The following list gives the names of a number of books and memoirs which may 

 be consulted with reference to the subjects treated of in this paper. They are 

 arranged in the order in which they appeared : — 



Bojanus, • De Foetus Canini velamentis.' ' Mem. Acad. Scien. St. Pe'tersbourg,' 



torn. v. 1815 ; 'Isis,' 1818, p. 616. 

 G. Cuvier, 'Sur les Enveloppes du Foetus.' ' Memoires du Museum,' torn. iii. 181 7. 

 Bojanus, • De Foetu Canino 24 dierum.' ' Nova Acta,' torn. x. 1821. 

 Rudolphi, ' Embryo der Affen.' ' Abhandlung. Berlin Akad.' 1828. 

 Von Baer, ' Untersuchungen iiber die Gefassverbindung zwischen Mutter und 



Frucht.' 1828. 

 C. G. Carus, 'Tabulae Anatomiam Comparativam Illustrantes,' iii. and v. 183 1- 



1840. 

 Mayer, * Nabelblaschen und Allantois.' ' Nova Acta,' torn. xvii. pi. 2. 1834. 

 Weber, * Die Verbindung zwischen Mutter und Frucht.' Froriep, ' Notizen,' 



996, bd. 46, Oct. 1835. 

 Eschricht, ' De Organis quae respirationi Foetus inserviunt.' Hafniae, 1837. 

 Von Baer, Entwickelungsgeschichte,' vol. ii. 1837. 

 Owen, ' Hunterian Catalog\ie, Phys. Series.' 1840. 

 Sharpey, 'Muller's Physiology, translated by Baly.' 1842. 

 Bisclioff, ' Kaninchen-Ei.' 1842. 

 Bischoff, ' Entwickelungsgeschichte Saugethiere und Menschen.' 1842. French 



translation by M. Jourdan, ' Encyclop. Anatom.' 1843. 

 Milne-Edwards, ' Sur la Classification Naturelle,' 'Annates Scien. Natur.' ger. 3. torn. 



i. 1844. 

 Goodsir, ' Anatomical and Pathological Observations.' 1845. 

 Bischoff, ' Hunde-Ei.' 1 845. 



Breschet, ' Sur la gestation des Quadrumanes,' ' Mem. de l'lnstitut/ torn. xix. 1845. 

 Weber, 'Zusatze zurLehre' (of the year 1835), 'Abhandlung. Jablon. Gesell.' 1846. 

 Coste, 'Histoire du DeVeloppement des Corps organises.' 1847. 

 Kilian, 'Die Structur des Uterus.' Henle's ' Zeitschrift.' 1849. 

 Barkow, 'Zootomische Bemerkungen.' 185 1. 

 Ecker, 'Icones Physiologicae.' 185 2-1859. 

 Bischoff, ' Meerschweinchen-Ei.' 1852. 

 Virchow, 'Ueber die Bildung der Placenta.' 1853. Reprinted in his 'Gesam- 



melte Abhandlungen,' p. 779. 

 Bischoff, 'Rehe-Ei.' 1854. 



