ANCULA. 



determining most points of importance, and in ascertaining that the internal structure 

 bears out its relationship to Idalia on the one hand, and to Tolycera on the other. 



The oral channel is very short ; it opens externally on the inferior surface of the head, 

 and leads to a buccal organ, which is well developed, compact, and muscular, though of no 

 great size ; and has connected with its upper surface a gizzard, constructed in the same 

 manner as in Idalia and Goniodoris. The tongue is long and narrow, having from twenty-five 

 to twenty-seven rows of spines ; there are four spines in each row, those next the median line 

 being large, excessivelybroad, and flat, with their inner margins denticulated; the external spines 

 are much smaller and plain; there is no central spine. The posterior portion of the tongue is 

 tubular, and protrudes a little from behind the buccal organ in a sheath. The buccal lip is 

 provided with a very formidable, spinous prehensile collar, (PI. 17, fig. 7), which is wide, and, 

 narrowing upwards, terminates on each side of the median line in a sharpish point. The spines, 

 (fig. 8) are arranged in indistinct transverse rows ; they are simple, curved, and much larger 

 than is usual in the Nudibranchs. 



The oesophagus is very long and slender : it has on each side, as it passes from the 

 buccal organ, a small, oval, salivary gland, which pours its secretion into the mouth through 

 a very short duct. At its origin, the oesophagus is swelled out into a crop, with delicate walls ; 

 it then suddenly contracts, and in the form of a constricted tube, passes through the nervous 

 ring ; immediately afterwards it again dilates a little for a short distance backwards, and 

 contracting once more, is continued as a simple tube to the anterior border of the liver, into 

 which it plunges on its way to the stomach. This latter viscus is small, and is buried just 

 within the frontal margin of the hepatic organ. The intestine is given off from its upper 

 surface, and, passing up through the liver, crosses over to the right side in front of the heart, 

 and, after a short course, terminates in the anal nipple, within the branchial circle. There is 

 a glandular enlargement of the intestinal tube just after it emerges from the liver, which is 

 apparently the same as that which has been designated a rudimentary pancreas in Doris. The 

 liver, of a yellowish brown colour, is rounded behind and truncated in front, and passes back- 

 wards beyond the branchiae ; the anus being situated comparatively further forward than 

 usual. 



The reproductive organs resemble, in the arrangement of their parts, those of Goniodoris, 

 and the other Bolycerin(B. The three component parts of the testis are not very distinctly 

 marked ; the glandular or fusiform portion exceeding the tubular only a little in caliber. The 

 vaginal tube and spermathecse are small. 



A delicate pericardium contains a ventricle and an auricle, and below it is the portal 

 heart. The ventricle gives off in front, in the usual manner, a large artery, which branches to 

 the various organs- ; and there is a folliculated glandular body, overlying the genitalia, which 

 ■is apparently connected with the arterial system, and is probably similar to that described in 

 Boris, as situated in the vicinity of the oesophageal ganglia. 



The branchial leaflets exhibit, in a high state of development, that curious internal struc- 

 ture, which in Boris we consider as an elastic apparatus to aid respiration by keeping the 

 gills, to some extent, in a state of expansion when out of water ; and such an apparatus would 

 seem of peculiar advantage to Ancula cristata, as it lives between tide-marks, and is liable to 

 be left dry by the receding tide. In this species, the apparatus in question is formed of a 

 double row of roundish vesicles, set on a central stem, and is situated in the trunk and prin- 



