28 SUMMARY OF CUERENT RESEARCHES RELATING TO 



death in many chick embryos, and various forms of abnormalities in 

 the nervous system of others. Excessive temperatures hastened the 

 development, while low temperatures retarded their rate of growth. 

 The seventy-two-hour chicks did not outgrow any of the abnormalities 

 produced in them at an earlier stage of development. Temperatures 

 •'between 103° and 108° F. produced 90 p.c. abnormal embryos. Of these 

 abnormalities 46 Ip.c. were in the head region, 54: p.c. in the neural 

 tube. In eggs incubated at 9-1° to 101° F., 67 p.c. were abnormal. Of 

 these abnormalities 17 p.c. were in the brain region, 83 p.c. in the 

 neural tube. Incubating eggs at normal temperatures showed nearly 

 ■6*5 p.c. of abnormalities, many of which were different from the 

 ■deformities produced under abnormal temperatures. J. A. T. 



Development of Opossum. — Carl Hartman {Proc. Amer. Soc. 

 Zool. in Anat. Record, 1919, 15, 351-2). In blastocysts of about 

 sixty cells (abont twenty-four hours) certain cells in the formative 

 half grow larger and migrate into the cavity, forming the primordium 

 of the endoderm. They multiply and flatten out against the inner 

 -Surface of the ectoderm. The mesoderm also arises by migration from 

 the undifferentiated superficial layer, forming to begin with a roundish 

 group in the mid-sagittal plane of the embryonic area. J. A. T. 



Fenestral Ear Plate in Caudate Amphibia. — H. D. Reed {Proc. 

 Amer. Zool. Soc. in Anat. Record, 1919, 15, 350). The manner in 

 which the structural elements combine to form the definitive fenestral 

 plate in the ear capsule of tailed Amphibians suggests a division of the 

 ■order into two legions. The author points out that the perfected 

 apparatus could have been useful only in terrestrial environment, and 

 holds that the living forms which are now aquatic are secondarily so. 



J. A. T. 



Dicephalic Pig. — J. M. Thuringer {Anat. Record, 1919, 359-67, 

 10 figs.). Records of dicephalic monsters mostly refer to calf and man. 

 The author describes monosomus diprosopus in a pig foetus. There 

 were two separate cerebral and cerebellar regions, and two fused medullse 

 oblongata?. An account is given of the skull, auditory apparatus, and 

 other parts. J. A. T. 



Double Ureters in Pig and Man. — A. G. Pohlman {A7iat. Record, 

 1919, 369-73, 3 figs.). The state of affairs in two pigs with evident 

 ureteral duplication or diverticula is compared with cases in man. The 

 ■double ureter has a certain embryological importance in that it furnishes 

 a clue to the disappearance of the cloacal segment of the Wolffian duct, 

 .and its manner of incorporation into the bladder. J. A. T. 



Split Fore-brain in Sheep Embryo. — E. Bujard {Rev. Suisse 

 Zool., 1918, 26, 245-307, 2 pis., 14 figs.). Of two separate twin- 

 embryos of the sheep, one showed a complete fissure of the prosence- 

 phalon (encephaloschisis). This malformation seemed to be due to an 

 amniotic strand which had prevented coalescence of the two sides of the 

 cerebral vesicle. Other malformations were associated, and their 

 morphological interest is very carefully discussed. J. A. T. 



