28 THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITAXNIAE. 



yolk-like bodies, possibly as a reserve food-stuff to tide the newly-born young over the 

 first few days of its independent existence. 



This late appearance of yolk-like globules, if they are not actually identical with 

 true yolk, seems to me to be a fact of some interest. 



In P. capensis, Balfour (2) described the gastral epithelium of the adult as con- 

 sisting of much elongated fibre-like cells attaining a maximum height of nearly '-5 mm. 

 He says " the cells are mainly filled with an immense number of highly refracting 

 spherules, probably secretory globules, but held by Grube, from the fact of their 

 dissolving in ether, to be fat 1 ." Balfour goes on to say, " The epithelial cells are 

 raised into numerous blunt processes projecting into the lumen of the stomach." But 

 in his Figure 20, Plate XVIII, the gastral epithelium is represented with a smooth 

 inner surface. 



With regard to the embryos of P. capensis, Sedgwick says : — " In Stage G the 

 endoderm is reduced to a layer of extreme tenuity. It soon, however, begins to 



increase in thickness The nuclei are placed in the deeper parts of the 



layer, and the protoplasm stains deeply and contains a large number of granules 



In old embryos the enteron generally contains a deeply-staining material with a number 

 of highly retractile particles in suspension. This substance is probably a secretion of 

 the endoderm cells." Sedgwick adds that the alimentary canal in free-living adults is 

 "permeated by a .number of similar highly refracting bodies." The granules referred 

 to by Sedgwick are indicated in one of his figures as somewhat irregular bodies — 

 that is to say, irregular like sand-grains, not like seed-grains. I do not know whether 

 the word granule means a body like a small grain of sand or like a small seed. 

 But there is a considerable difference between these two interpretations, and it is very 

 desirable to be precise. For my present purpose I make a mental distinction between 

 globules, spherules and granules, using the last term in the sense of minute irregular 

 bodies, or mere points. 



By globules I refer to the bodies described above in late embryos of P. novae- 

 britanniae which vary much in size between a minimum and a maximum. 



By spherules are intended minute round bodies of generally uniform size. 



I have seen Balfour's spherules in P. capensis and also in post partum young of 

 P. leuckarti and P. novae-britanniae. They react towards staining media differently 

 from my globules. They do not take the eosin nearly so readily as do the latter. 



In his well-known work on the histology of Peripatus, Gaffron is absolutely reticent 

 about the histology of the gut. Was it because he could not understand the appearances 

 presented ? 



Unfortunately I cannot give any decisive account of what does actually take place. 

 This could only be attempted with an abundance of fresh material at one's disposal. 

 But enough may be said to show that the subject is one of singular interest. 



From what I have seen I am led to the conclusion that Balfour's account of 

 the gastral epithelium of Peripatus is only true of one phase — a periodically recurring 

 phase — in the life-history of Peripatus. There are long periods during which Peripatus 



1 The yolk-like globules in late embryos of our species were not dissolved after 4 hours' treatment with 

 chloroform. 



