1890.] A. Alcock— On the Gestation of Elasmohranch Fishes. 51 



II. — Natiiral History Notes from H. M/s Indian Marine Survey Steamer 

 ' Investigator,' Commander Alfred Carpenter, R. N., D. S, , 

 commanding. — No. 14. Observations on the Gestation of some Sharks 

 and Bays. — By Alfred Alcock, M. B., Surgeon-Naturalist to the 

 Marine Survey. 



[Received November 18th, 1889 ; — Read January 1st, 1890.] 



(With Plate I.) 



The observations which I have to record were, of necessity, made so 

 hurriedly that I can only hope them to be regarded as a gleaning in the 

 outskirts of the field of bionomic science. But any one who, single- 

 handed, and almost without appliances, has been called upon, at a 

 moment's notice, to undertake the examination of large dead animal 

 bodies in the plains of tropical India will readily realize the difficulties 

 which hinder the exact and exhaustive dissection, under similar condi- 

 tions, of huge fishes, on board ship, in the Bay of Bengal. And I trust 

 that the drawbacks alluded to will be taken into consideration with the 

 unfinished appearance of the work. 



§ 1. Observations on the Gestation of Carcharias melanopterus, 

 Zyg^na blochii, and Carcharias dussumieri, 



a. Carcharias melanopterus. A female, five feet long, was cap- 

 tured by Mr. W. H. W. Searle, of the ' Investigator,' on the Orissa coast, 

 off the entrance to the Chilka Lake, on the 21st January, 1889. Tlie 

 abdomen was much distended ; and, on opening it, the distal ends of the 

 oviducts were found to form, on each side, an enormously dilated uterus, 

 each occupying the whole length of the abdominal cavity on its own side. 



On section, the walls of the uteri were found to be hyperaemic, 

 rather hypertrophied, and spongy : their cavities were divided off, each 

 into three separate longitudinal compartments : and tightly-packed in 

 each compartment, lying head forwards, parallel with the antero- 

 posterior axis of the mother, was a young one twelve inches long. Each 

 young one was, further, completely enveloped in a very delicate mem- 

 brane, on removal of which the placental-cord was found to be extended, 

 in a semi-spiral curve, from a point midway between the pectoral fins 

 of the foetus to its maternal attachment at the hinder end of the uterus. 



Each placental cord, which is about eighteen inches long, and 

 one-sixth of an inch in diameter, is seen to divide, near the maternal 

 attachment, into two equal branches, each of which subdivides again 

 and again to form a compact arborescent mass, which is closely ap])lied 

 to a flat vascular disk on the wall of the uterus, and thus the placenta 



