Natural History of the Shark. 365 



It contained bloodj and I believe it to be an auxiliary heart de- 

 signed for circulating the blood in the appended organ. A 

 similar structure exists in the same situation in the Thornback 

 and Torpedo. 



" In the sac of the gland a cream-like secretion was found, and 

 the same flowed out pretty copiously through the excretory ducts 

 when pressure was applied to the gland. * * * The blood in 

 the pulsatoiy cavity, from which it is probable that the secretion 

 just mentioned is formed, coagulated like ordinai-y blood on ex- 

 posure to the air, but it was more dilute." * * * 



" How the anal appendages are constituted in Sharks, I cannot 

 speak from my own observations, having yet examined these 

 organs only in one instance, that of Scyllium Edwardii. From 

 the descriptions of naturalists, it may be inferred that they vaiy 

 more or less in organization in different genera ; that in some, 

 as probably in the genus Carcharias, there is a distinct gland, 

 secreting an opake fluid, similar to that of the Rays I have 

 mentioned ; that in others, as in the genus Scyllium, the gland 

 is wanting, and its place is supplied by a sac (one for each organ) 

 situated under the common integument of the lower part of 

 the abdomen, communicating by a narrow elongated passage with 

 the appendage, and containing a fluid slightly viscid, probably 

 secreted by follicles situated between the fibrous inner coat and 

 its outer muscular one*." 



Dr. Davy ends these notices with a probable solution of the 

 controversies that have prevailed from the days of Aristotle on 

 the functions of these accessoiy organs. Aristotle had observed 

 that they were characteristic of males and peculiar to Cartilaginous 

 Fishes. Bloch, the most authoritative name among modern 

 naturalists, held the conclusion that the organs were designed 

 for prehension ; but Dr. Davy considers their purposes explained 

 in an ancient remark that they were used as retaining members. 

 The report in the days of Aristotle was that the male and 

 female Shark coupled like dogs : " Sunt qui se vidisse confirmant 

 nonnulla ex cartilagineis aversa modo canum terrestiium co- 

 hserere." (De Hist. Anima. lib. v. cap. v.) 



I venture on making only one observation on the facts detailed 

 by Dr. Davy. The structure of the anal appendages, with the 

 gland here said to perform the function of an auxdiary heart, is 

 found existing in the Carcharias, a viviparous, while it is wanting 

 in the Scyllium, an oviparous Shark. Though largely developed 

 in the Torpedo, a fish eminently viviparous, the foetus being 

 without any investing membrane whatever, a character it par- 

 takes with the Squatina, usually denominated the Shark-ray 

 from its intermediate structure, both rhomboidal and elongated, 

 * Davy's Researches : Phys. and Anat. vol. ii. chap, xix. ''■'""' 



