120 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



There are, however, other facts which favor this view. The transverse furrows upon the outer 

 .sides of the lamella? are obviously comparable with the grooves upon the cirri. We also note 

 that each lamella possesses a nerve extending throughout its length which has essentially the 

 same structure as the nerve of a cirrus; it has a like complete investment of ganglion cells, 

 although these are not collected into ganglia; beside this, the nerves of the lamellae arise from 

 the same ganglion as the nerves of the. cirri, and it is impossible to distinguish the nerves of 

 cirri and lamella 3 before they arrive at their respective terminations. The nerves of the lamella 1 

 arc simply the innermost of the series arising from the ganglia. 



The arrangement of the muscles of the lamella? is according to the same plan as is that of 

 the cirri. We have also noted that the sensory organs at the bases of the outer lamellae have a 

 tendency to be simpler or less developed than those between the inner lamellae. 



The number of both lamella? and cirri is quite variable, but the number of lamellae does not 

 seem to bear any constant relation to that of the cirri. The entire number of lamellae and cirri 

 borne by the inferior labial lobe is about forty. 



The facts stated seem to indicate that the lamellated organ is composed of a number of 

 slightly modified labial tentacles, and is not a structure developed upon the labial lobe separately 

 from the tentacles. Furthermore, there are indications that the outer members of the series of 

 lamella? and the inner members of the series of tentacles graduate into each other, possibly 

 being developed in one direction in some individuals and in the opposite direction in other indi- 

 viduals. 



The inferior labial lobe of a half-grown female showed an interesting condition in the 

 development of the lobe. The superior labial lobes were as well developed, proportionally, as 

 in a mature specimen. The inferior labial lobe, on the contrary, was in a rudimentary condition. 

 It reached only about to the middle of the buccal mass. Each side of the anterior edge of the 

 lobe was produced in a curve; in the center were a number of tine lamellae. The tentacles at 

 the edges of the lobe were very rudimentary, in many eases apparently not yet being differ- 

 entiated into cirrus and sheath. 



Haswell makes the following statement: "One of the six or eight female specimens 

 examined by me presents a condition of the median minor tentaculiferous lobe which may, per- 

 haps, have a bearing on the functions of the part. In this specimen, which was a good-sized 

 one and fully developed in other respects, the lobe in question (the group of lamella?) was repre- 

 sented by a rudiment, in which, however, all the parts of the perfected structure were distinctly 

 and symmetrically represented." 



C. — Inner Tentacles of the Male. 



The arrangement which we see when we open the cephalic sheath of the male is quite dif- 

 ferent from that which we have observed in the female. The buccal cone occupies the same 

 relative position in both sexes. At each side of and dorsal to the buccal cone of the male is a 

 group of tentacles closely resembling the superior labial tentacles of the female. (Fig. 7; Text- 

 tig. 4.) They are borne upon two lobes which are elevations of a ridge of the base of the 

 cephalic sheath nearly encircling the buccal cone. The ridge is very low dorsally and ventrally 

 to the tentacle lobes, which latter rise to a height of from 1£ to 3 centimeters. Ventrally the 

 ends of the ridge approach each other like the tips of a horseshoe and end upon the cephalic, 

 sheath near the innermost digital tentacle. This ridge obviously corresponds to the similar 

 ridge of the female which bears the superior labial lobes, and we shall also term these tentacle- 

 bearing lobes of the male superior labial lobes. 



Outside the ventral ends of the ridge bearing the superior labiai lobes are two groups of 

 tentacles, one at each side of the head, which do not appear in the female. There are four ten- 

 tacles in each group. (Fig. 7, Sp, ASp; Text-tig. -i, S, AS.) The tentacles of the right-hand group 

 do not differ markedly from the tentacles of the superior labial group. The tentacles of the left- 

 hand group, however, are enormously developed and form a conspicuous organ known as the 

 spadix. The smaller corresponding group of the right side is called the antispadix. 



