ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 159 



throughout the whole length of the tube, except in Rhyncotus rufescens, 

 and perhaps in other Tinarniformes where the tubes are divided into 

 two zones of cells of quite different aspect. The excretory nipple, in- 

 vested by the fine integument, encloses the excretory canals of the lobes 

 with the terminal portions of their enveloping capsules. Its extremity 

 may be naked or furnished with plumules or exceptionally with feathers. 

 Within it, as whhin the capsules, there are often very large capsules of 

 Herbst and abundant adipose tissue. There may be bundles of smooth 

 muscular fibres forming two constricting groups, one at the apex, the 

 other at the base of the nipple, the two connected by sparse longitudinal 

 fibres. The arteries which supply the gland arise from two trunks 

 issuing from the caudal artery. After a variable course, at some point 

 of which they anastomose with vessels from the next interapophysary 

 spaces, these arterial trunks break up into two or three branches, which 

 are distributed throughout the gland. The two coccygeal veins arise 

 directly from anastomosis of the hypogastric veins, or from a trunk 

 rapidly dichotomized. They follow the same course as the arteries. The 

 nerves arise from branches, issuing between the first and second caudal 

 vertebras, which after dividing anastomose with sympathetic nerves. 



The investigator gives a detailed account of the development of the 

 gland (in Anas boscas), as well as of the chemical composition of its 

 secretion, and of physiological experiments undertaken to prove its 

 function. The general result of these experiments is that the gland is 

 of no use for increasing the impermeability of the feathers, has no toxic 

 action — at least in this country — and that its removal or hypertrophy 

 has no effect whatever on the health of the bird. In origin, develop- 

 ment, anatomy, etc., the uropygium of birds presents marked analogies 

 with the odoriferous glands of other Amniota, especially with those of 

 reptiles, and it must therefore be regarded as an odoriferous gland. 



The paper includes a synoptic table of the state of the gland in 

 different groups. 



Plastosomes of Visual Cells.*— G. Leplat has studied the differen- 

 tiation of the plastosomes in the rods and cones of the bird's eye. 

 Definite plastosomes seen in the embryonic cells and in the visual cells 

 undergo chemical change and differentiation in the primordia of the 

 rods and cones. Some granulations persist in the internal segment ; 

 others, in the external segment, form a homogeneous sheath on the , 

 centrosomic filament. 



Minute Structure of Amnion of Chick. f — Tiberius Peterfi has 

 studied the epithelial cells of the chick's amnion. The young cells 

 become vacuolated. The fibrils appear as a haptogen-membranous 

 boundary between the vacuoles. Lainellse become reduced to a reti- 

 culum of fibrils which extend continuously over the whole amnion, 

 without it being possible to define beginnings or ends. The stronger 

 lines become cell-boundaries, the finer form intracellular fibrils. 



* Anat. Anzeig., xlv. (1213) pp. 215-21 (5 figs.). 

 f Anat. Anzeig., xlv. (1913) pp. 161-73 (8 figs.). 



M 2 



