1891.] Uterine Villiform Papillce of Pteroplatsea micrura. 365 



:>phonemata can only pass down the pharynx of the embryo. The 

 only other external communications of the pharynx, namely, the 

 mouth and gill-clefts, are firmly closed, the opposite margins of the 

 2xternal gill-clefts being in the most complete apposition. There are, 

 3nsequently, no branchial filaments. 



The trophonemata are narrow, strap-shaped processes of the uterine 

 lucosa which widen very slightly and gradually from their base to 

 about the middle of their length, whence they taper still more gradu- 

 ly to their rounded apex. Those which enter the pharyngeal cavity 

 )f the foetus are the longest of all, measuring from 18 to 20 mm. in 

 ensrth and about 1'4 mm. in extreme breadth. Save for the presence 

 jf a blunt thickening that traverses them in a somewhat sinuous 

 jurse from base nearly to apex, tapering and branching as it goes, 

 id standing out in fairly bold relief from both their surfaces, they 

 ippear quite flat. 



Stained in borax- carmine, mounted in spirit, and viewed under a 

 low power by reflected light, they present a minute, honey- combed 

 ippearance of their surfaces due to the presence of innumerable 

 small depressions. From the ap pressed conjunction of ridges which 

 rand these, a slightly elevated polygonal network results. 

 Transverse sections of a trophonema shew that these depressions 

 the funnel-shaped mouths, narrowing below into the lumina, of 

 lall, short, bulb-shaped glands of the same simple tubular type as 

 seen, for example, in the crypts of Lieberkuhn, or, better still, in 

 the gastric glands of anthropotomy. 



The glands are arranged perpendicular to the surface, side by side, 

 the substance of the mucosa into which they are, in fact, so many 

 involutions of the investing epithelium so that the bases of those of 

 opposite sides are separated from one another only by blood vessels 

 id a very meagre, if any, connective tissue. 



Vertical sections of a trophonema in planes parallel to its surface, 

 jr, in other words, transverse sections of groups of glands, shew that 

 lese are so closely packed as to be polyhedral by appression. 

 For a certain distance from the base of the trophonemata the de- 

 pressions are small and simple, but they soon become larger and 

 ampound, each being then the common mouth or short duct of a 

 little group of glands, just as in the human stomach, wnere one 

 leets with simple glands, each with its independent opening, and 

 rith groups of glands opening into a common depression of the 

 lucous surface. 



The larger (secondary) depressions, it is obvious from an attentive 

 study of the surfaces of several trophonemata, as well as from, trans- 

 rerse sections, have resulted from the further depression of the smaller 

 (pi-imary) depressions in groups ; and the raised margins of the 

 former result from the coalescence of those portions of the margins 



