ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 575 



to have only half the normal number of chromosomes. The paternal 

 contributions have dropped out. The size of the nuclei is also reduced 

 to about a half. When foreign spermatozoa that have been suljjected 

 to rajs enter the ova, the disharmony that might be expected does not 

 occur, the reason being that the development is really parthenogenetic, 

 the sperui-nuclei disappearing. 



Reproductive Organs of Fishes.* — A. Lickteig has investigated a 

 number of points. The Petromyzonts have two true abdominal pores, 

 which represent the openings of the body-cavity into the urogenital 

 sinus. The Selachians and Salmonids (males included) have also paired 

 pores, or rudiments of them— ruptures from the body-cavity outwards. 

 But only in Petromyzonts are they exits for the genital products. 



In Salmonids of both sexes there is a new kind of genital pore. It 

 occurs in all female Teleosts. It is a constricting off of a portion of 

 the coelom to form an efferent duct. In Salmonids this remains as an 

 open genital funnel in permanent communication with the ccelom. In 

 other Teleosts it is closed off from the coelom to form a wide ovarian 

 cavity. 



In female Teleosts there are no independent oviducts. Portions of 

 the ovarian sacs serve as oviducts, and are fused terminally. But they 

 have no direct relation to Miillerian ducts. 



Development of Cranial and Visceral Skeleton in Lamprey.f — 

 Alban Schalk has reached a very interesting conclusion, which, if con- 

 confirmed, is likely to excite considerable interest. While the cranial 

 skeleton is mesodermic in origin, the visceral skeleton is definitely 

 ectodermic. The branchial skeleton is ectodermic, as Dohrn and Piatt 

 have also concluded. But as the skeleton of the appendages is 

 beyond doubt mesodermic, it does not seem as if it could be regarded 

 as homodynamous with the branchial skeleton which is ectodermic. This 

 is therefore strongly against Gegenbaur's theory of the derivation of 

 paired limbs from the branchial skeleton. 



Central Sensory Organs in Petromyzon.| — D. Tretjakoff finds a 

 sensory organ in the bipolar intra-ependym cells of the spinal cord of 

 larval and adult lamprey. There is also a sensory organ in the infundi- 

 bulum and in the recessus praeopticus. It consists of bipolar cells, the 

 body of which is mostly extra-ependymal, though the central processes 

 show that the cells are really iutra-ependymal. It is probable, as Dendy 

 has suggested, that Reissner's fibre has a function like that of an otolith. 

 The condition of things in the lamprey is compared at length with that 

 in the lancelet, where the central sensory organs of the spinal cord are 

 well known. 



Subcutaneous Vascular System of Amphioxus.§ — B. Mozejko 

 gives a fine account of the vascular system of Amphioxiis, and in par- 

 ticular of an intricate subcutaneous system. The whole system is closed 



* Zeitschr. wiss. Zool., cvi. (1913) pp. 228-88 (3 pis. and 9 figs.). 



t Arch. Mikr. Anat., Ixxxni. (1913) Abt. 1, pp. 43-67 (1 pi. and 34 figs.). 



+ Arch. Mikr. Anat., Ixxxiii. (1913) Abt. 1, pp. 68-117 (2 pis.). 



§ MT. Zool. Stat. Neapel, xxi. (1913) pp. 65-103 (1 pi. and 2 figs.). 



