ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
763 
normal it is clear that irregularities of cleavage have no appreciable 
effect on any stage of development of the embryo. 
Vascular Papillae in Discus proligerus of Capra.* — Dr. C. Crety 
describes vascular papilliform diverticula from the follicular theca, 
which penetrate more or less into the follicular epithelium in that zone 
which is in immediate connection with the discus proligerus. The 
histogenetic processes consist in a proliferation of the elements of the 
tunic of Henle and in the formation of new elements between the tunic 
of Henle and the fibrous tunic. It may be that the papillae, which are 
rich in blood-vessels, facilitate the nutrition of the ovum. 
Development of the Squirrel.f — Dr. E. Fiserius gives an account 
of the development of Sciurus vulgaris , which though it contains no new 
discovery, deserves to be recorded as a lucid corroboration of much that 
is old. 
Development of Bladder. J — Dr. W. Nagel has studied embryos of 
man, rabbit, guinea-pig, and cow, in order to elucidate the development 
of the bladder. His results do not harmonize with those of Keibel or 
of His. According to Nagel, the ureters which at first open into the 
Wolffian ducts gradually separate themselves from these, and come to 
open into the allantoic duct independent of, but at the same level as the 
Wolffian ducts. Thereafter there begins on the allantoic duct, above 
the opening of the four ducts, the development of the urinary bladder, 
and the ureters being loosed from all connection with the Wolffian ducts 
have their openings gradually shunted upwards until they attain their 
final position. 
Development of the Pancreas. § — Herr O. Hamburger finds that 
the pancreas in man arises from two originally separate rudiments. 
The smaller, at first separate, subsequently opens along with the bile- 
duct, into the duodenum ; the larger opens nearer the pylorus. In the 
second half of the second month of foetal life the two rudiments anasto- 
mose. The small duct of Santorini in the adult is not the duct of the 
smaller pancreas-rudiment, but arises from a portion of main rudiment, 
lying between the intestine and the region where the two rudiments 
coalesce. 
Dentition of Young Edentata. || — Dr. C. Rose has investigated the 
development of the teeth in embryos of Dasypus novemcinctus, D. Jiybridus , 
Manis javanica, and Myrmecophaga , and comes to the general conclusion 
that the dentition of Edentates is due to degeneration from a more 
highly organized type. The enamel, as is well known, is very rudi- 
mentary. In Dasypus novemcinctus (Tomes, Kiikenthal, Rose), D. villo- 
sus (Kiikenthal), D. Jiybridus (Rose), Orycteropus capensis (Pouchet and 
Chabry), two sets of teeth are represented in the embryo. Like Kuken- 
thal, Rose believes that the milk dentition of mammals is no new acqui- 
sition, but a phyletic inheritance, and derivable in all likelihood from 
the compression of several reptilian-like teeth-series into one. As 
* Atti (Rend.) R. Acead. Lineei, 1892, pp. 402-8 (4 figs.). 
t Yerh. Physik-med. Gesell. Wurzburg, xxvi. (1892) pp. 103-22 (1 pi.). 
% SB. K. Preuss. Akad. d. WiSs., 1892, pp. 177-81. 
§ Anat. Anzeig., vii. (1892) pp. 707-11 (3 figs.). 
|| Tom. cit., pp. 495-512 (14 figs.). 
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