ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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literature, and describes in detail a particular case which he was able to 
investigate. This tail was 7 cm. in length and 2 cm. in circumference ; 
it included no bone nor cartilage, but fibrous tissue, fat, nerves, blood- 
vessels, and striped muscle. 
Placenta of Carnivora.* — M. M. Duval has a somewhat lengthy and 
detailed account of the placenta of the bitch, which is the first part of 
his contribution to our knowledge of the placenta of the Carnivora. It 
contains little matter of general interest, and we must be content to draw 
attention to its publication. 
Development of B] adder and Allantois in Guinea-pig. f — Dr. F. 
Keibel finds that the cloaca in the embryo guinea-pig is divided on the 
eighteenth day by two lateral folds into an anterior region, the rudiment 
of the bladder, and a posterior region into which the rectum opens. By 
“ cloaca ” the author means, as he carefully explains, the space which 
His calls bursa pelvis — the space into which there open in early stages 
the gut, the Wolffian ducts, and the duct of the allantois, and into which 
at a later stage the ureters and genital ducts also open through the 
urinogenital sinus. The depression from the ectoderm which appears 
in the position of the anal membrane Keibel calls the anal groove ; it 
corresponds to the proctodseum. The nature of the growth which sepa- 
rates the cloaca into two regions is then explained. From the rudiment 
of the bladder the urachus buds out, and a proper endodermic allantois 
extends to the placenta and there expands into a small vesicle. Dr. Keibel 
also maintains that in Mammals and Man the renal bud and the renal duct 
arise from the archinephric duct. 
Development of Teeth in Chamseleon.J: — Dr. C. Bose has investi- 
gated by means of serial sections the development of teeth in Cliameeleon 
vulgaris. He finds that the teeth are never replaced, although a well- 
developed supplementary ridge exists. New teeth are, however, formed 
throughout life behind those already existing. The teeth fuse with the 
bone of the jaw. The odontoblasts of the fang gradually pass into 
the osteoblasts of the jaw-bone, and in consequence the dentine passes 
over into bone by means of an intermediate tissue, which has the tubules 
of the one and the bone-cells of the other. 
While the anterior teeth of the chammleon are simple cones, the 
hinder “ molars ” are three-pointed. As in Mammals, these teeth arise 
from several papillae which are closely apposed. Whereas, however, 
in Mammals the cylindrical cells of the enamel epithelium proper are 
continuous over all the papillae, in the Chamaeleon each papilla has a 
separate layer of epithelium. The fusion of the papillae takes place 
later ; in one case the author succeeded in finding a fully formed tooth 
in which the two anterior tooth-projections had fused, while the third 
still stood isolated. These facts support the author’s theory that the 
complicated teeth of Mammals are formed by the fusion of simple teeth. 
According to the author’s previous investigations, the so-called dental 
germ and the enamel organ are only a part of the epithelium of the 
jaw which has sunk in. In most Fishes and Amphibians, and also in 
* Journ. Anat. et Physiol., xxix. (1893) pp. 249-340 (3 pis.) ; pp. 425-65 (2 pis.). 
t Anat. Anzeig., viii. (1893) pp. 545-54 (5 figs.). 
i Tom. cit., pp. 566-77 (8 figs.). 
