134 SUMMARY OF CUEEENT EESEAECHES RELATING TO 



various periods during development at an abnormal temperature, and 

 compared the size of the larvae with that of others allowed to grow 

 normally. He was thus able to prove that the permanent effect of tem- 

 perature on the growth diminished rapidly and regularly from the time 

 of impregnation onwards. Exposure to about 8° C. for an hour at the 

 time of impregnation ju'oduced an average diminution of 4*1 p.c. in 

 the size of the larvae measured after eight days' growth ; by exposure 

 during the 4th hour after impregnation a diminution of about 1*2 p.c. 

 was brought about; during the 15th hour about 0-2 p.c. Exposure to 

 about 22° produced an increase in size, about 1*1 p.c. for each hour's 

 exposure in the 4th hour; to 0*4 in the 14th; to 0*13 in the 46th; 

 and to 0-01 in the 120th hour. 



Exposure to a temperature of 26° during the first few hours of 

 development produced a diminution of from 20 "8 to 7 - 4 p.c, but in 

 the later hours an increase of 4*3 to 11-0 p.c. The reaction of the 

 organism to a constant environmental condition was thus a variable one. 

 Tins is probably explicable by the fact that the temperatures necessary 

 to kill the organisms, and presumably also those which cause an un- 

 favourable effect on growth, rise steadily during development. Thus 

 the death temperature is about 28 '5° for unsegmented ova, 34° for 

 blastulae, and 40° for plutei. The impregnated ova were also found 

 to be much more sensitive to changes in the salinity of the water during 

 the early stages of development than during the later ones. 



Accelerating Effect of Heat upon Growth.* — Prof. T. W. Gallo- 

 way has experimented with developing ova of Rana sylvestris, Ambly- 

 stoma jjunctatum, and Bufo americana, which were subjected to three 

 different temperature conditions, but without other food than that con- 

 tained in the egg and the surrounding albumen. He sought to discover 

 whether the increased growth due to raised temperature is brought about 

 by accelerated imbibition of water or by increased anabolic metabolism. 

 So far as the results go, they point to the conclusion that it is chiefly 

 the imbibitory process which is accelerated by heat. 



Production of Double Embryos from Newt's Eggs.f — Dr. W. Ton- 

 koff has done tor the ova of Triton tseniatus what O. Schultze and 

 G. Wetzel have done for frogs' eggs. The artificially fertilised ovum 

 is placed in a drop of water on a glass plate, with glass bars of suitable 

 thickness on each side; the animal pole comes as usual to the top; a 

 covering plate, fixing the egg, is laid on ; and the whole is turned 

 through 180°, bringing the animal pole to the underside. In a variable 

 number of cases this results in dvijlicitas ventralis or lateralis, as the 

 author describes in detail. 



Experimental Embryology.* — Dr. G. Cutore finds that by varnish- 

 ing the eggs of the common fowl, in whole or in part, it is possible 

 to produce anomalies of development, especially as regards the central 

 nervous system. He describes in detail the various malformations pro- 

 duced, compares them with similar appearances noted by various authors 

 in incubated eggs, and assigns as a common cause the insufficient aera- 

 tion of the eggs. 



* Amer. Nat., xxxiv. (1900) pp. 949-57 (6 figs., 4 tables). 

 t SB. Preuss. Akad. Wisa., 1900, pp. 794-7 (1 tig.), 

 j Anat. Anzeig., xviii. (1900) pp. 391-414 (12 tigs.X 



