422 Mr. A. Alcock on 
By careful focusing we find that the entire capillary net- 
work and the edge of the trophonema in which 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 what 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 apply only to the specimen under description. 
In the Mahdnadi 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. 
In 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 elandular follicles which have next to be described. 
We also see (5) sections of capillaries round the arteries and 
between the glands. 
§ 4. The 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 tropho- 
nema; there are none at the edge of the trophonema where 
the arterial loop runs. They are somewhat club-shaped and 
lie close together, being separated from one another, those of 
the same side by capillary channels, and those of the opposite 
faces of the trophonema by the central vein and by the deep 
capillaries, as well as by a small amount of connective tissue. 
They lie in pocket-like depressions, and show (in section) 
the following structure :—(1) a broadish vestibule, lined by 
short columnnar 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. 
