ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 447 



Locke's solution. Amitosis occurred, involving the nucleus only, not the 

 cell-body. Mitotic division of the binucleate cell sometimes followed the 

 amitosis of the nucleus. 



Chromosomes in Fowls." — M. F. Guyer finds a large curved chro- 

 mosome, which he regards as bivalent, in the primary spermatocytes of 

 the testes. The same occurs in many cells of female embryos. The 

 males are regarded as homozygous, and the females as heterozygous for 

 sex and sex-linked characters. 



Regeneration of Mesencephalon in Larval Amblystoma.t— H. 

 Saxton Burr finds that regeneration of nervous tissue follows the re- 

 moval of the right eye and the underlying mesencephalon. The tissue 

 is similar to that normally found, except that important optic areas are 

 lacking. Removal of the mesencephalon only, the eye being left, is 

 followed by almost complete regeneration of the optic lobes. It is 

 inferred that functional activity of the end-organ normally connected 

 with the brain affords the necessary stimulus to regeneration of the part 

 of the brain removed. 



Histology of Poison-glands of Bufo agua.| — P. G. Shipley and 

 <T. B. Wislocki distinguish in the skin of this tropical toad those 

 glands which produce adrenalin and those whose secretion contains 

 none of that substance. The adrenalin-producing acini are limited to 

 the glandular masses behind the eye and surrounding the typanum, 

 known as the " parotid " glands, the chromaffin reaction being negative 

 in all other cutaneous glands. The contents of the poison-glands having 

 been discharged, probably through the contraction of a smooth muscle- 

 coat surrounding the gland acinus in response to a stimulus of sufficient 

 strength, the emptied sac does not refill, but is resorbed, its place being 

 taken by an immature gland of the same type. These young glands bud 

 from the duct or neck of the older gland-sac, about which a ring of them 

 may be found. They grow downward through the various strata of 

 the cutis vera, carrying with them a layer of tissue from the outer 

 loose layer of the dermis, and are surrounded by it throughout. The 

 secretion of these poison-glands is produced by and during the de- 

 struction of the cytoplasm of epithelial elements lining the acinus of 

 the young gland, the destruction leaving only a cell-nucleus within the 

 acinar wall. 



Two kinds of secretion occur in the lumen of the mature poison- 

 gland : — 1. A granular secretion, which is the first to be formed, and is 

 found filling the entire lumen of the young glands, and is located in the 

 central part of the mature acini. 2. A clear homogeneous or finely- 

 punctate fluid filling the periphery of the lumen, which takes on a 

 bright yellow colour after fixation in fluids containing chromates. This 



* Biol. Bull., xxxi. (1916) pp. 221-68. 



t Proc. Soc. Ext'er. Biol. Med., xiii. (1916) pp. 180-1. See Physiol. Abstracts, 

 i. (1916) No. 8, p. 349. 



X Carnegie Inst. Washington, Contributions to Embryology, iii. (1915) No. 9, 

 pp. 73-90 (2 pis.). 



