126 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



secretion. The region of the cell immediately about the nucleus is entirely free from any secre- 

 tion, so that the outer edge of the tubule shows a clear border in sections. Figure 57 A shows a 

 single cell of the secretory epithelium drawn with the aid of a camera lucida. It was taken from 

 a place where the epithelium was lower than ordinary, but otherwise is characteristic. The single 

 row of deeply staining granules almost completely tills the body of the cell. The bent base of 

 the cell is a very characteristic feature, although not found universally. The short basal portion 

 of the cell is directed upward and inward, and the longer outer portion of the cell is perpendicular 

 to the axis of the tubule. As the neck of the gland is approached a change takes place in the 

 character of the epithelial cells. The epithelium becomes lower and the cells contain fewer and 

 smaller granules. Finally the epithelium is only of about half the height of that in the tubules; 

 the granule secreting cells disappear, and ordinary goblet mucous cells are found scattered in the 

 epithelium, which is of the same character as that clothing the surface of the slime gland between 

 the pores of the glands. 



At the edge of the slime gland are all stages between fully developed tubular glands and the 

 merest invaginations of the surface epithelium. One might almost say that there is here an onto- 

 genetic series in the development of the glands. The smallest invaginations are lined with epithe- 

 lium entirely similar to that upon the surface of the slime gland. Farther from the edge the 

 invaginations become deeper, and from the inner parts outgrowths occur which become the 

 glandular tubules of fully developed glands. The young tubules possess an epithelium like that 

 of the adult in its essential characters, but at first only a few cells appear to be glandular. These 

 are typical goblet cells tilled with finely granular secretion. In more developed glands the 

 secreting cells become more numerous, the granules of secretion are larger, and finally all the 

 cells below the neck of the gland are filled with coarse granules. 



The description of the glands upon the outer side of the antispadix was referred to this place. 

 They are of the same character as those of the slime gland of the spadix, but are less developed. 

 The glandular epithelium and the secretion are apparently alike in both organs. The glands 

 upon the sheath of the antispadix are proportionately shallower and are less branched than those 

 of the spadix, but otherwise the structure seems to be the same, 



FIRST CIRRUS OP THE SPADIX. (FIG. 15.) 



The first cirrus is much the largest of the four forming the spadix. It is nearly circular in 

 section, gradually diminishing in size from the base to near the tip. The latter diminishes in size 

 very rapidly, causing the cirrus to end in a point like the tip of a low cone. The tip is frequently 

 excentric and is sometimes produced like a nipple. The surface of the cirrus is smooth except 

 near the tip, where very faint annular grooves may be noticed. The base of the cirrus, its largest 

 part, measures 32 millimeters dorso-ventrally and 17 millimeters from side to side. It is 6 centi- 

 meters in length. 



From the ventral side of the base a strong muscle passes ventrally and across the body, to 

 become lost in the tissues of the opposite side of the cephalic sheath. The main mass of the 

 tissue of the cirrus passes immediately into the tissues of the posterior portion of the cephalic 

 sheath on its own side. The development of a special muscle for this cirrus, as well as the 

 remarkable muscular development of the cirrus itself, indicates that the cirrus is very actively 

 employed at some time or other in the animal's existence, and it may also indicate that the 

 cirrus is extended or retracted as a whole from its base and is not extensile in the same manner 

 as the cirri of other tentacles; but all statements of how this and the other cirri of the spadix 

 are used are as yet guesses, pure and simple. 



Transverse and longitudinal sections explain the rest of the structure of this cirrus. (Figs. 52 

 and 53.) Near the center of the cirrus, but still to the inner side of it (i. e., the side nearest the 

 buccal mass), is the large nerve N. This is surrounded by the transverse musculature of the 

 cirrus. Around the core of transverse muscles is a thick ring of longitudinal muscles, which are 

 divided by radial septa of transverse muscles. Outside this follow three thin layers of muscle — 

 a circular, an outer longitudinal, and an outer circular layer. The essential features of the 

 arrangement of the musculature are therefore the same as those of the digital or labial cirri. 



