422 Mr. A. Alcock on 



By careful focusing we find that the entire capillary net- 

 work and the edge of the trophonema in whicli the arterial 

 loop runs are covered by a layer of pavement epithelium. 

 With very little teasing in glycerine the arterial loop can be 

 cleanly stripped from the rest of the trophonema, except at 

 the very tip. 



This, then, is wliat is seen on simple examination of a 

 magnified trophonema — a pair of lateral arterial pillars 

 meeting to form a long narrow arch, a central venous column 

 standing in the middle of the archway, and a superficial 

 lattice-wall of capillaries enclosing the whole. From this 

 point of view a trophonema is simply a long compressed cone 

 of blood-vessels. 



It must be particularly mentioned that the dimensions 

 above given ajiply only to the specimen under description. 

 In the ]\lahanadi specimen the trophonemata were shorter 

 and very much finer and more delicate. And it may be 

 broadly stated that in all the species of Batoids hitherto 

 examined in this connexion on board the ' Investigator ' the 

 trophonemata vary in size with every individual. 



Jn a transverse section of a trophonema we see (1) the 

 sections of the artery standing out on each side like a pair of 

 ears, (2) the large vein occupying the centre, and, arranged 

 almost in a ring round the vein, close together (and perpen- 

 dicular to (3) the sections of the superficial capillaries), (4) 

 a number of glandular follicles which have next to be described. 

 We also see (5) sections of capillaries round the arteries and 

 between the glands. 



§ 4. llie Glands of the Uterine Villi, or Trophonemata. 



As above implied, the glands occupy only the middle part 

 of a section — about the middle two thirds of a transverse 

 section made anywhere through the basal half of a troplio- 

 noma ; there are none at the edge of the trophonema where 

 the arterial loop runs. They are somcu hat club-shaped and 

 lie close together, being separated from one anotiier, those of 

 the same side by ca})illary channels, and those of the o|)posite 

 faces of the trophonema by the central vein and by the deep 

 ca})illaries, as well as by a small amount of connective tissue. 

 They lie in pocket-like de})rcssions, and show (in section) 

 the following structure : — (1) a broadish vestibule, lined by 

 short columiniar epithelium, and (2) an usually double bulbous 

 base (the gland proper), each bulb consisting of a compact 

 wedge of large broad-based tapering cells arranged like the 

 coats of an onion in vertical section. 



