A SOUTH AMERICAN SPECIES OF PERIPATUS. 345 



rouud the embryo, and that it is then gradually divided into 

 two patches, one in front, the other behind the embryo. 



The most noticeable point about the uterus of Peri pat us 

 is that the contained embryos, which are from eight to ten 

 in number, are all at different stages, the youngest near the 

 ovary being perhaps in the segmentation stage, while the oldest 

 will be completely formed and ready to be born. 



All my specimens were collected at one season of the year 

 (i. e. November and December), so I am unable to say whether 

 they are pregnant all the year round, but it seems probable 

 that this is the case. In this relation Peripatus imthurni, 

 as also P. torquatus and Edwardsii, differ from the South 

 African and New Zealand Peripatus, in which cases the de- 

 velopment of the embryos, though going on all the year rouud, 

 commences at one particular season, so that all the embryos 

 found in the uterus of the female are approximately of one age. 

 The structure of the uterus of Peripatus will be best seen by 

 examining figs. 1 and 5. 



Fig. 1 represents a longitudinal section through a piece of 

 uterus not far removed from the ovary. At e is seen a youno- 

 embryo lying in a cavity of the uterus, this cavity, which is the 

 widened lumen of the uterus, is difficult to trace in front and 

 behind, though in some places remnants of it can be detected; 

 but on the whole it is generally obliterated. 



The outer wall of the uterus is formed by a very slightly 

 differentiated single layer of cells (c), which though distinctly 

 nucleated are without cell walls, so that they cannot be 

 separated from one another very easily. Within this is the 

 uterine epithelium, which simply consists of a mass of proto- 

 plasm in which is embedded a large number of nuclei. Slight 

 traces of cell walls can be seen in fig. 5, which is a transverse 

 section of a young embryo with its surrounding uterus. The 

 inner line of the uterine epithelium is folded, so that it has a 

 crinkled appearance (ck.) ; this is, doubtless, for the purpose of 

 increasing the absorption surface, and it is by means of this 

 crinkled appearance that the boundary between the uterus and 

 embryo can be always detected. This folding of the inner layer 



