ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 391 



few first spermatocytes succeeded in passing through synapsis and sub- 

 sequent division with more or less of an appearance of normality. 



An accessory chromosome or a;-element of the guinea-fowl (maternal 

 species) type was present. The x-element is of large size in the common 

 fowl, and consequently the mature spermatozoa without it are much 

 smaller than the ones which bear it. It is suggested that inasmuch as 

 males are produced only from eggs fertilized by a spermatozoon without 

 the 2;-element, the great preponderance of males among such hybrid off- 

 spring may be due to the simple fact that the smaller type of spermatozoon 

 can more readily penetrate a foreign and hence more or less incompatible 

 egg-plasm. 



Spermatogenesis in Opossum.* — H. E. Jordan finds in the nuclear 

 cycle of the male germ-cells in Didelphys virginiana an odd or unpaired 

 (differential) chromosome, which appears to be comparable in form and 

 behaviour to the heterotropic or accessory chromosome of the Tracheata. 

 It is probably the larger member of the spermatogonial (duplex) group 

 of seventeen. It determines a dimorphism of spermatids, one type with 

 five chromosomes, the other with four (which resolve into nine and eight 

 respectively). It is lost (permanently for the spermatogenetic process) 

 in the reticular phase of the resting spermatid. 



There is evidence of a side-by-side union of the chromatic loops 

 following a primary end-to-end union. If the essence of the synapsis 

 is intermingling of the fundamental elements of the chromosomes, then 

 this double method of conjugation would seem more effective in pro-- 

 ducing this result than either telo- or para-synapsis alone. 



The mitochondrial elements which contribute to the formation of 

 the spiral filament of the intermediate piece of the spermatozoon are 

 traced back to the late growth period of the primary spermatocyte, where 

 they appear to arise as true chromidia. A detailed account is given of 

 the structure of the mature spermatozoon. 



Spermatogenesis of Horse.f — S. Kirillow describes the structure of 

 the tubuli contorti of the testis, Sertoli's elements (nuclei embedded in 

 a syncytium), twelve stages in the spermatogenesis, and the phenomena 

 of synapsis. 



Development of Orbital Glands. J— N. I cewenthal has studied the 

 early stages in the development of the lacL.ymal gland, the glandula 

 infraorbitalis and the orbitalis externa, the Harderian gland, and the 

 nictitating gland. The glandula infraorbitalis is not the so-called infra- 

 orbital that opens into the mouth in the rabbit for instance, nor the so- 

 called glandula orbitalis s. zygomatica of the dog, but a gland partly 

 internal to, partly above the jugal, which opens into the posterior (ex- 

 ternal) portion of the conjunctival sac. 



Development of Teeth in Soricidse. —Augusta Arnbiick-Christie- 

 Linde finds evidence of more than three incisor-germs in both jaws of 



* Arch. f. Zellforschung, vii. (1911) pp. 41-86 (3 pis. and 2 figs.). 

 t Arch. Mikr. Anat., Ixxix. (1912) pp. 125-47 (1 pi. and 1 fig.). 

 t Arch. Mikr. Anat., Ixxix. (1912) pp. 464-563 (2 pis.). 

 § Ann. Mag. Nat. Hist., ix. (1912) pp. 601-25 (2 pis.). 



