314 PROFESSOR ROLLESTON ON THE 



Observations on the Figures. 



Fig. 1. Shows the placenta of the Tenrec (Centetes ecaudatus) detached from the deci- 

 duous serotina, shown in fig. 2, and from the utero-placental area covered with 

 persistent or non-deciduous serotina, shown in fig. 3. Part of the amnios (a) 

 and of the umbilical cord (u c) are left in connexion with the placenta (pl). 

 The umbilical vessels are prolonged up into an upstanding rim of membrane, 

 oh', which is itself an upward prolongation of the chorion, and was con- 

 tinuous with the uterine tissues along a parapet of membrane, u p, in fig. 3. 



Fig. 2. Deciduous serotina of Tenrec. It is separated both from placenta, fig. 1, and 

 from the uterine structures figured in fig. 3. It is but of wafer-thickness, and 

 centrally it has many perforations for the uterine vessels. In the natural 

 condition of the parts its periphery would have been in connexion with the 

 inner periphery of the circular area of corrugated mucous membrane seen iu 

 next figure, and one of its surfaces would have been in relation with the 

 uterine aspect of the placenta, and the other with the foetal aspect of the 

 persistent non-deciduous serotina, ps, fig. 3. 



Fig. 3. Utero-placental area of Tenrec : u p represents the parapet of uterine mucous 

 membrane with which the chorionic upgrowth (ch', fig. 1) was continuous. 

 Within this limitary line is a quoit-shaped area of mucous membrane con- 

 centrically corrugated ; and within it again we have a space much perforated 

 by orifices of blood-vessels, and covered with the non-deciduous or persistent 

 serotina, p s. The presence of the ring of corrugated mucous membrane 

 bounding the non-deciduous serotina, and bounded itself by the circular 

 parapet (u p) of mucous membrane, and the presence of an upgrowth of the 

 chorion (ch') continuous with this parapet, are phenomena, so far as is known 

 by me, unique in the Mammalia. 



Fig. 4. Section of placenta (pl) with part of chorion (ch) of Guinea Pig {Cavia aperea). 

 Upon the uterine surface of the placenta there is an upgrowth, pl', the 

 " Kern" of BischofF (Meerschweinchen-Ei, 1852, pp. 43 & 44), the texture of 

 which is to the naked eye somewhat looser than that of the larger mass, pl, 

 of which it is morphologically and histologically but a part. In the angle 

 between its outer border and the upper surface of the placenta is seen a small 

 piece of membrane, f, which, in the natural state of the parts, was continuous 

 with a process (g) of deciduous serotina, which is seen in the next figure. 

 Near to the place of attachment of this process of membrane are seen the cut 

 orifices of vessels belonging to the " sinus circularis" system, for which see 

 KoUiker, /. c. pp. 140, 147, or Robin, I. c. p. 130. 



Fig. 5. Section of the part of the uterine cornu and of the deciduous serotina which 

 was in connexion with the placenta of the preceding figure. The deciduous 



