110 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



the ventral surface of the cephalic sheath. The eyes are situated partly within the angles 

 between the auricles of the hood and the upper portions of the just described posterior faces of 

 the cephalic sheath. 



In the ventral surface of the cephalic sheath is a broad and deep channel, into which tits the 

 dorsal part of the funnel. (Text-fig. 2; PI. 3, Fig. 3.) The anterior edge of the sheath, in line 

 with the channel, is deeply notched, so that ventrally the tentacles of the two sides are widely 

 separated. (Figs, 24 and 25.) Partly surrounding and extending back from the edges of the 

 ventral notch in the cephalic sheath of the female is the exception previously noted to the 

 complete smoothness of the inner surface of the cephalic sheath. (Figs. 24 and 25.) We see here 

 a large number of low, narrow, glandular lamella' extending parallel to each other from side to 

 side of the area. The lamellae of the anterior half of the organ frequently radiate from centers at 

 each side of the notch in the sheath. Consequently, while their median portions extend trans- 

 versely to the axis of the body, the lateral portions turn more or less sharply forward. The 

 posterior lamella? do not reach the centers referred to, and so the forward bend at the sides 

 becomes less and less pronounced as the back of the area is approached. Finally the most poste- 

 rior lamella? are almost straight. 



Considerable differences exist in the shape of this area in different specimens. The one 

 which I have described and figured in Fig. 24 seems to be (mite rare, although for a considerable 

 time I thought it to be the normal shape. Instead, the lamella? rarely meet at such centers as I 

 have figured. The differences in the descriptions of various authors suggest that practically the 

 only constant feature may be the presence of numerous lamella-, while their arrangement is 

 capable of a high degree of variability. Frequently the area is nearly or quite separated into 

 two portions by a median furrow. Valenciennes and Lankester refer to the organ as a paired 

 structure. Owen describes it as consisting of " two clusters of soft conical papillae, and on each 

 side of these a group of lamina' disposed longitudinally". 



As noted, the organ, as it may fairly be called, exists in the female only. Slight folds of 

 the skin are often found in tin- same region of the male, but they are evidently adventitious. 

 resulting from contraction, and do not in any way represent a structure similar to the one 

 possessed by the female. 



The lamella? of the female form an organ for the retention of the spermatophore. In the 

 case figured (Fig. 25) the spermatophore is arranged with unusual symmetry. In no other 

 instance was it so nicely coiled as in this, though it was always spread out upon the surface of 

 the lamella? so that few coils overlapped. The coils of the spermatophore were in all cases so 

 firmly glued to the lamella? that it was impossible to remove them without breaking either 

 lamella? or spermatophore. Kerb mentions that in his specimen the spermatophore was 

 partly embedded in the coagulated secretion of the lamellae. The secretion has not been so 

 noticeable in my own specimens, being only sufficient to hold the spermatophores, but that very 

 tightly. 



Having considered the digital tentacles as a complex, the cephalic sheath, let us now consider 

 their individual structure. It has been noticed that each tentacle comprises two parts, namely, a 

 slender retractile cirrus and a tough sheath within which the cirrus may lie entirely withdrawn. 



The completely extended cirri are often fully twice the length of the sheaths. They are 

 supple and slender, tapering slightly to a bluntly rounded point. Average dimensions of the 

 larger cirri would be In centimeters in length by 4 millimeters in diameter. Each cirrus presents 

 throughout its length, except the basal portion, a series of narrow annular grooves and ridges. 

 (Fig. 50.) These vary in number according to the length of the cirrus. Upon a cirrus of 

 ordinary length there are 50 to 60 ridges. The cirri are ordinarily three sided in the portion 

 which is commonly extended outside the sheath, the broadest and flattest side being turned 

 inward toward the mouth. Exceptional cirri which are round are quite common, and in any 

 case the outer angle of the cirrus is much rounded, and the portion which remains inside the 

 sheath is always nearly round, being flattened only slightly upon the inner side. Willey states 

 that the outer sides are dee)i In-own in color, while the inner side is of a pale neutral tint. A 



