HISTOLOGY AND DEVELOPMENT OF MYRIOTHELA PHEYGIA. 52l 



the elaboration of the secretion product which occupies the 

 expanded portion of the cell. In the upper part of the goblet- 

 cell zone the endoderm is composed of goblet-cells lying 

 wedged between the apices of palisade-like cells exactly 

 resembling those occurring in the ciliated zone, except in the 

 fact that they now abut on the free surface. When this 

 portion is retracted the deep folds present the appearance in 

 sagittal sections of long tubular glands, which, from the 

 character of the abundant goblet-cells, closely simulate the 

 crypts of the large intestine. 



In the middle and lower part of this region the endoderm is 

 thrown up into low conical villi. These structures are char- 

 acteristic of the whole of the endoderm with the exception of 

 the part already described, that is in the neighbourhood of the 

 mouth, and in the foot. They vary very much in length in 

 the diflFerent regions of the animal, but are usually longest in 

 the lower portion of the tentacle-bearing region, where they 

 are long filiform structures, sometimes branched, and may 

 measure "3 to '5 mm. from base to apex. Generally speaking, 

 the villi are not muscular, but in the goblet-cell region they 

 appear to have a distinct muscular axis. 



Structure of a Villus from the Goblet-cell Zone. 



A section through the axis of one of these is shown in 

 fig. 16. On the sides of each villus, and between their 

 bases, we have the same arrangement of palisade-cells and 

 goblet-cells as that described above. At the apex, however, 

 are a group of cells presenting many new features. These 

 I propose to call the apical cells, and they form not only 

 the apex of the villus, but are also continued downwards as its 

 muscular axis. 



Each apical cell has the following general structure. The 

 protoplasm is abundant, and stains deeply, thus offering 

 a marked contrast to the other cells of the villus. It is 

 also turbid and opaque, but differs very much in this and 

 in its behaviour with stains in different parts of the cell. 

 In the muscular stem, however, the protoplasm is always 



