[139] Loc. cit.
[140] Loc. cit.
[141] Professor Lieberkühn (Gesellschaft zu Marburg, Jan. 1876) finds in Mammalia a bilateral arrangement of the mesoblast, which he compares with that described by me in Elasmobranchii. In Mammalia, however, he finds the two masses of mesoblast connected by a very thin layer of cells, and is apparently of opinion that a similar thin layer exists in Elasmobranchii though overlooked by me. I can definitely state that, whatever may be the condition of the mesoblast in Mammalia, in Elasmobranchii at any rate no such layer exists.
[142] Loc. cit.
[143] Quart. Journ. of Microsc. Science, Oct., 1874. [This Edition, No. V.]
[144] “Embryologische Studien an Würmern u. Arthropoden.” Mémoires de l'Acad. S. Pétersbourg. Vol. XIV. 1873.
[145] Archiv für Mikr. Anat. Vol. VII.
[146] Jenaische Zeitschrift, Vol. IX. 1875. A bilateral development of mesoblast, according to Professor Haeckel (loc. cit.), occurs in some Osseous Fish. Hensen, Zeit. für Anat. u. Entw. Vol. 1., has recently described the mesoblast in Mammalia as consisting of independent lateral masses.
[147] Archiv für Mikr. Anat. Vol. XI.
[148] A protoplasmic network resembling in its essential features the one just described has been noticed by many observers in other ova. Fol has figured and described a network or sponge-like arrangement of the protoplasm in the eggs of Geryonia. (Jenaische Zeitschrift, Vol. VII.) Metschnikoff (Zeitschrift f. Wiss. Zoologie, 1874) has demonstrated its presence in the ova of many Siphonophoriæ and Medusæ. Flemming (“Entwicklungsgeschichte der Najaden,” Sitz. der k. Akad. Wien, 1875) has found it in the ovarian ova of fresh-water mussels (Anodonta and Unio), but regards it as due to the action of reagents, since he fails to find it in the fresh condition. Amongst vertebrates it has been carefully described by Eimer (Archiv für Mikr. Anat., Vol. VIII.) in the ovarian ova of Reptiles. Eimer moreover finds that it is continuous with prolongations from cells of the epithelium of the follicle in which the ovum is contained. According to him remnants of this network are to be met with in the ripe ovum, but are no longer present in the ovum when taken from the oviduct.