ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1':'." 



Centrifuging Eggs of Wood Frog.*— A. M. Banta and B. A. 

 Gortner have "centrifuged " embryos of Raria sylvatica at the blasto- 

 pore stage, subjecting them to 1850 times the pressure of gravity for 

 two minutes. All the survivors show an accessory tail-like appendage 

 or several (2-4) accessory tails. These occurred along the mid-ventral 

 region and had a typical tail-like structure. In some " centrif uged " 

 eggs of Amblystoma, the front end of the head of the larva, some- 

 times back as far as the gill, failed to develop. The hereditary 

 determiners for development work out their destined end only when 

 maintained in certain appropriate spatial relations. 



Typical Sex-ensemble in Mammals.j — D. Berry Hart uses the 

 term sex-ensemble for the gonads, the urinogenital tract, the opposite 

 sex-duct elements, and the secondary sexual characters. The whole 

 tract is like clearly written manuscript with a palimpsest portion 

 partially erased. The non-potent part in the female includes the 

 epoophoron and paroophoron ; in . the male, the hydatid testis and 

 prostatic utricle. 



The germ-cells (or " heredity cells " of -the author) arise from the 

 zygote at an early stage, and are intruded into the somatic part of the 

 sex-gland. It is supposed that they are of two kinds, one set with 

 Wolffian determinants, one without. It is supposed that sex is de- 

 termined at fertilization : a "Wolffian spermatozoon and a non-Wolffian 

 ovum resulting in a male-producing zygote, a non-Wolffian sperma- 

 tozoon and a Wolffian ovum resulting in a female-producing zygote. 



The development of the female genital organs may be thus 

 summarized : — 



Organs. Source. 



Heredity cells . . . Early division of zygote. 



Somatic part of ovary . . Genital ridge and connective-tissue of 



Wolffian body. 



Fallopian tubes, uterus, and Mullerian ducts, 

 vagina (upper two-thirds). 



Lower third of vagina . . Upper part of urinogenital sinus and 



lower ends of Wolffian ducts. 



Hymen .... An organ of the urinogenital sinus, and 



derived from the Wolffian ducts. 



Vestibule .... Lower part of urinogenital sinus. 



External genitals . . . External region on and below pubes (im- 



perfectly worked out). 



Bladder .... Anterior division of endodermal cloaca ; 



fundus allantoic. 

 Urethra .... Upper part from the urinogenital sinus, 



also lower part, but it is re-tunnelled. 

 Ureter .... Upward growth from Wolffian duct. 



Kidney .... 'Upward growth, in great part from 



Wolffian duct ; an upper part from 



Wolffian body. 



* Year-took, Carnegie Inst. Washington, xiii. (1914) p. V21. 



t Edinlurgh Med. Journ., July and Aug. 1914, pp. 1-47 (5 pis.). 



