636 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the action of gravity and also that of a constant centrifugal force. Its 

 motion is constant and extremely irregular. Eggs which had been kept 

 in constant motion from the moment of their removal from the toad 

 till placed in the machine developed normally and produced normal 

 embryos. In fact, they developed faster than those outside, a feature 

 which appears to be due to the agitation of the eggs yielding better 

 aeration. The effect was very different from that of a centrifugal force, 

 which kills the eggs outright. 



Influence of Radium-Rays and Radium-Emanation on Develop- 

 ment and Regeneration.* — A. Schaper has experimented with develop- 

 ing embryos of frog and with regeneration in Planarians and newts, in 

 order to detect the influence of radium-rays and radium-emanation. 

 The experiments established a disruptive and tissue-disturbing effect, 

 and the frequent occurrence of abnormalities. 



Rudimentary Amnion in Selachians.f — T. D'Evant describes, 

 in some very early stages of Pristiurus and Scyllium, which show the 

 medullary groove and gut tube still open, two laterally placed double 

 folds of the extra embryonic ectoderm. They run in the direction of 

 the longitudinal axis, and extend towards but do not reach the mid- 

 dorsal line. In the cranial region the folds meet ; in the caudal region 

 they become lower and disappear. The author regards these folds as 

 a rudimentary amnion. 



Development of Liver in the Pig.J — David C. Hilton discusses 

 the early morphogenesis and histogenesis of the liver in the pig, with 

 notes on the development of the ventral pancreas. 



The most interesting deviation of the results of this research from 

 those of other investigators concerns the relations of the vascular system 

 in the septum transversum to the trabeculation of the glandular struc- 

 tures derived from the primitive " protonic " wall. A second important 

 difference concerns the method and direct results of the gland -formative 

 proliferation. The hepatic tissue, instead of being grown into by the 

 vessels, grows out and extends among and around them, although by 

 virtue of increases in calibre, the vascular spaces actively change the 

 location of the rods springing from the protonic wall. 



Breeding Habits of Yellow-Bellied Terrapin.§ — H. M. Smith 

 notes that the nest of Pseudemys rugosa is usually made in sandy loam 

 or sandy clay, flask-shaped, about 4 in. deep by 4 in. wide at the 

 bottom, with an opening somewhat smaller than a silver dollar. All 

 the eggs (10 to 35) are laid at once, and packed tightly by the mother. 

 The egg-laying is in June and July, and the young remain in the nest 

 until the following spring. Birds, especially crows, destroy some eggs. 

 The male is smaller than the female, his claws are twice as long as hers, 

 and the under shell is flat, while in the female it bulges slightly. 



Hybridisation of Triton marmoratus and Triton cristatus.|| — 

 W. Wolterstorff has succeeded in effecting hybridisation between Tr. 



* Anat. Anzeig., xxv. (1904) pp. 298-314 (4 figs.;. 



t Op. cit., xxiv. (1904) pp. 490-2. 



% Trans. Amer. Micr. Soc, xxiv. (1903) pp. 55-88 (4 pis.). 



§ Smithsonian Misc. Collections, xlv. (1904) pp. 252-3. 



|| Zool. Anzeig., xxviii. (1904) pp. 82-6. 



