228 Transactions. — Zoology. 



anterior to the level of the bursa Entiana the diameter suddenly diminishes, 

 the uterine portion of the oviduct passing into the Fallopian portion (f.t). 

 Each Fallopian tube passes forwards, dilates into an oval oviducal gland 

 (o.gl, supposed in the figure to be seen through the liver), this narrows 

 again, curves round the side of the gullet to its ventral wall, where it turns 

 backwards, unites with its fellow, and the common tube thus formed opens 

 into the coelum by a single trumpet-shaped aperture (/.*')• This median 

 common portion of the Fallopian tubes is connected with the ventral body- 

 wall by a vertical sheet of peritoneum or falciform ligament. 



The Fallopian tube has its mucous membrane produced into longitudinal 

 ridges : in the uterus these become, as it were, frayed out at their edges, 

 forming longitudinal rows of long villi provided with very large and obvious 

 vascular loops. These serve to furnish a supply of oxygenated blood to the 

 embryos which are retained in the uteri until fitted for independent 

 existence. 



The specimen examined was a gravid female, the two uteri containing 

 together ten foetuses. The presence of the oviducal glands in this form 

 indicates clearly that the viviparous condition is a secondary one, since the 

 function of these glands is the secretion of the horny egg-shell. In this 

 connection it is worthy of remark that the oviduct contained yellowish- 

 brown silky shreds, quite like those found on the undeveloped egg-shell in 

 the skate, and evidently representing a rudiment of that structure. Accord- 

 ing to Balfour* the egg of Mustelus, Galeus, Carcharias, and Sphijma, is at 

 first enclosed in a delicate shell : if this is the case in Scymnus the shell 

 must be thrown off at a very early period. 



5. The nervous system and sense organs. 



The brain presents several points of interest. It is much elongated 

 owing to the great length of the medulla oblongata and thalamencephalon, 

 the optic lobe and cerebellum having the usual proportions (see fig. 7-10). 

 The medulla oblongata (m. o) is considerably wider than the spinal cord, 

 and presents above a long shallow fourth ventricle (v. 4) : at its anterior end 

 it is produced dorsally into large restiform bodies (r. b). 



The cerebellum (cb) has a regularly oval outline ; its dorsal surface is 

 marked by a median longitudinal groove, and it is connected with the 

 medulla at about the middle of its length by large cerebellar peduncles (pd). 

 It contains a large cavity, the cerebellan ventricle or metacccle (cb. v), which is 

 in free communication below by a central aperture with the fourth ventricle. 



The mid-brain has the usual structure, consisting of a ventral portion, 

 the crura cerebri (c.c) and of paired dorsal elevations, the optic lobes (o.l) ; 

 it contains a large cavity in free communication behind with the fourth 

 ventricle, which may be called the mid-ventricle or mesocmle (ni.v). 

 * " Comp. Embryology," vol. ii., p. 33, 



