SEA-FISHERIES LABORATORY. 203 



006 mm. thick, and consists of several fairly well marked 

 layers. Next the external surface is a thin layer of 

 dense connective tissue fibres, and then a layer of rather 

 loose areolar tissue containing round cells. Next the 

 internal surface is an epithelium consisting' for the most 

 part of rounded cells, in places suggesting a cubical 

 epithelium. For the most part it is broken down, but 

 here and there are indications of the presence of mucous 

 cells. Two such are shown in the figure containing large 

 " goblets." This layer doubtless represents the remains 

 of an epithelium which has secreted the mucus filling 

 the cyst, and has been almost entirely disintegrated by 

 the shedding of its products. Between these two layers 

 is a broad one consisting of connective tissue fibres 

 running round the cyst. Some of these are straight, but 

 the majority are greatly twisted. 



Fig. 6, PL I, represents part of a section through 

 one of the cysts possessing a thick opaque wall. The 

 structure is obviously entirely different from that of the 

 thin-walled cysts. The most prominent element in it is 

 the mucous epithelium lining the interior — this is thrown 

 into folds and prominences resembling the villi of a 

 mammalian intestine. Part of one of these folds is 

 represented in fig. 7 as seen under an oil-immersion 

 lens, and fig. 8 represents a villus cut near its tip in 

 transverse section. The epithelium is a columnar one, 

 as is seen on the right in fig. T. As a general rule, 

 little of the layer exists in this condition, but here and 

 there are relatively large patches of the unmodified 

 columnar cells. For the most part, however, the 

 appearance is that suggested by fig. 7, that is a " goblet- 

 cell " epithelium. The '* goblets " are about 0'04 high, 

 and are quite typical in structure : one of them is shown 

 in fig. 7 with the section passing through its aperture. 



