542 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Poison-organ of Sting-ray.* — H. Muir Evans has made sections of 

 the poison-organ of Trygon pastinncea, first described by Porta in 1905 

 as lying in two grooves on the ventral surface of the sting. The gland 

 arises from a special layer of epithelium starting at the root of the 

 spine ; the secreting tissue consists of regular follicles with ducts and 

 central and lateral canals ; the secretion is discharged by means of 

 nipples or filaments projecting from the canals ; there is a layer of 

 muscular tissue surrounding the central canal ; the staining reactions 

 of the secretions are like those of the poison of the weever ; there is no 

 doubt as to the genuineness of the toxicity. 



Growth-rings on Herring-scales.f — G. W. Paget and R. E. Savage 

 contribute a note summarizing such additional evidence as they have 

 obtained from a fresh series of investigations with regard to the 

 structure and significance of the rings on herring-scales. Their studies 

 included a comparison of dorsal and lateral scales from the same fish ; a 

 comparison of the effect produced when the scale is examined under 

 polarized light with that obtained under ordinary conditions ; and an 

 examination of the ring in section. The investigations yield important 

 corroborative evidence of the truth of the view that the transparent 

 rings mark recurring periods of minimum growth. 



c. General. 



Fauna of Jordan System.^ — Nelson Annandale finds that this 

 fauna is mainly Pala^arctic, but with a distinct Ethiopian element, which 

 may be due to the existence in Pliocene times of a river flowing south- 

 wards into the Indian Ocean from what is now the Jordan system. 

 The Ethiopian system consists exclusively, or almost exclusively, of 

 fishes with great vitality and adaptiveness. The absence or paucity of 

 Ethiopian forms among the Invertebrates of the system may be due to 

 an obstruction of the outlet of the Lake of Tiberias and a fatal increase 

 of salinity. The Palrearctic element is composite and of comparatively 

 recent origin, consisting mostly of species from the north and east, but 

 also of a few of Nilotic origin. The northern and eastern Palasarctic 

 animals, in cases in which they had no powers of independent pro- 

 gression on laud, probably reached the system through floods or other 

 occasional agencies. The Nilotic species are mostly amphibious and 

 may have arrived on their own feet or wings. 



Cranial Muscles of Mammals.§ — F. H. Edgeworth gives an account 

 of the pharyngeal, laryngeal, and hypobranchlal muscles of Ornltho- 

 rhynchus and Echidna. He also discusses the development of these 

 muscles in Dasyurus viverrinus and some other ilarsupials, in the pig 



* Proc. Zool. Soc, 1916, pp. 431-40 (7 figs.). 



t Proc. Eoj'. Soc, Ixxxix. (1916) pp. 258-60. 



X Journ. and Proc. Asiatic Soc. Bengal, xi. (1915) pp. 437-76. 



§ Qnart. Journ. Micr. Sci., Ixi. (1916) pp. 383-432 (13 pis.). 



