1891.] Observations on the Gestation of Indian Rays. 203 



mucous membrane of the uterus is beset with, trophonemata, but with 

 the growth of the foetus the trophonemata become atrophied by 

 pressure, except opposite the spiracles of the foetus, where they re- 

 main as large bunches which penetrate through the spiracles deep 

 into the foetal pharynx. We find that where, as appears to be the 

 most common condition, two embryos occupy the uterus, the one is 

 rolled up within the other head to head and tail to tail but in such a 

 way as to leave the spiracles of the inner one exposed for the tropho- 

 nemata to enter. In one remarkable instance, where one spiracle of 

 the inner embryo was overlapped and concealed, that spiracle was 

 of diminutive size, while its fellow of the opposite side was much 

 enlarged. On microscopic examination we find the nutrient secre- 

 tion of the trophonemata lo contain numerous small granular bodies, 

 and a few large granular corpuscles which resemble leucocytes. 



In the pregnant female of Myliobatis nieuJiqfii we found three 

 young ones, two males and a female, of different sizes, in an uterine 

 enlargement which exists on the left side only. In the two smallest 

 there are very delicate external gills ; but of such structures there is 

 no trace whatever in the largest embryo. 



The spiracles in all are singularly large and patent, being kept 

 open by an eave-like extension of the cranial cartilage. The mucous 

 membrane of the uterus, which is thickly beset with long branched 

 glandular villi, was intensely vascular, had an odour, not of fish, but 

 like that of raw beef, and was covered with a creamy yellowish- 

 coloured fluid somewhat resembling " laudable pus " in appearance. 

 It may be mentioned that the spiral gut of one of the einbryos was 

 found to be full of the same creamy fluid, unchanged. Apparently 

 loose in the body cavity, in the largest foetus, were found strings of 

 bead-like concretions held together by inspissated albuminous 

 material : and on examination under the microscope these concre- 

 tions were found to contain numerous crystals of oxalate of lime and 

 dumb-bell-shaped bodies exactly resembling the dumb-bell concre- 

 tions of urate of ammonia found in human urine. 



As one of us has already described (' Journal Asiatic Society 

 Bengal,' voL 59, Part II, pp. 54 and 55) the general structure of the 

 uterus and uterine glands in the stage preparatory to pregnancy in 

 Myliobatis nieuhofii, we are deferring a report on this species in the 

 hope of obtaining ampler material to make the report more com- 

 plete. 



We devote this paper to some account of the phenomena of gesta- 

 tion in Trygon ivalga, in which we have been able to make fuller 

 observations. 



