ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 59 



undergo. This leads to the opening of the maternal vessels, and to the 

 iuterchorial or intervillous formation of lacunre, or " sangui-maternal 

 lakes." 



Egg-laying of Plethodon cinereus.* — W. H. Piersol describes the 

 deposition of the eggs in this Canadian salamander. Fertilization is 

 internal. The lips of the cloaca are pressed against the surface from 

 which the eggs will eventually hang (e.g. in a decaying log), and a small 

 quantity of mucus is extruded and adheres firmly to it. The extrusion 

 of each egg occupies about twenty minutes, and an interval of five to 

 ten minutes occurs before the next appears. Four to seven eggs were 

 laid in contact. As is usual among Urodela the outer envelope of each 

 egg; is of a much more sticky mucus than the inner ones. In Plethodon 

 the outer layer is unusually thin, and the deposition of the preliminary 

 mass of very sticky mucus is peculiar. One egg of small size is often 

 retained in the ovary and absorbed. If it is laid it develops normally. 

 One female, kept in a terrarium, swallowed two of her eggs (in process 

 of gastrulation), and regurgitated them three hours later — killed by the 

 disturbance. Swallowing spawn has been noted for many Amphibia, 

 usually when something has occurred to pervert the natural instincts. 

 Smith descril)es it as normal for CryptobrancMts, and in this case the 

 regurgitated eggs frequently continue to develop. 



Experimental Embryology. t — G. Cotronei has begun a series of 

 experiments on the developing eggs of frog and toad, which he has 

 subjected to the infiuence of solutions of various strengths of sodium 

 chloride, potassium chloride, magnesium chloride, lithium chloride, and 

 lithium sulphate. The developmental modifications induced are only 

 referred to in the present communication, which states the author's aim 

 of tackling experimentally the important problem of the relation between 

 correlation and differentiation. 



b. Histology. 



Identification of Tissues in Artificial Cultures. | — ^E. D. Congdon 

 has inquired into the different kinds of tissues that are produced in 

 artificial cultures. He has especially studied the origin of the common 

 cell strings, reticula and membranes, and gives some very striking figures. 

 A common type of reticulum with a corresponding membrane-growth 

 can be traced back to sub-pericardial reticulum in a six-day ventricle. 

 There is indirect evidence for a coarse reticular growth from the peri- 

 toneum of liver (five- and ten-day) and intestine (five- and ten-day), and 

 from the endocardium and pericardium of ventricle (five- to fourteen- 

 day). An unbroken sheet is found to arise from intestinal peritoneum 

 under certain conditions. 



Sectioned cultures of intestine (six-day) gave rise to a fine mesh 

 similar to that of ventricle reticulum. Mesenchyme is sometimes given 

 off from limb-buds (five- and ten-day) in the form of disorganized 



* Trans. R. Canadian Inst., xxiv. (1915) pp. 121-6. 



t Atti Rend. R. Accad. Lincei Roma, xxiv. (1915) pp. 1248-53. 



: Anat. Record, ix. (1915) pp. 343-59 (5 pis.). 



