GONIODORIS NODOSA. 



pointed tail, down the central ridge of which is a sulphur-yellow streak. Foot oblong, 

 rounded in front and pointed behind, of a bright rosy brown in the centre from the liver 

 appearing through. 



Calcareous spicula are imbedded in almost every part of the skin of this animal, but 

 nowhere crowded except in the oral tentacles and at the tail, where they form slightly ra- 

 diating, dense tufts : a few pass transversely over the back and across the foot ; they are 

 more numerous in the margin of the cloak and along the sides, forming two longitudinal 

 rows on each side, uniting at the tail. In the dorsal tentacles they are small and curiously 

 bent to suit the cylindrical form of these organs, in which they are placed crosswise. The 

 spicula of the body are rather large, crystalline, pointed at the ends and slightly bent in the 

 middle, and are covered with distant irregular nodulous rings. 



The pulsations of the heart are 72 in a minute. 



This species appears to be common on all parts of our coast. It is liable to some 

 variation, especially in the tubercles, which has given rise to several spurious species ; at 

 least such we are now inclined to consider them after a long and tolerably intimate acquaint- 

 ance with the several varieties. 



It may, however, be necessary to enter a little more into detail in justification of 

 this opinion, in which we unfortunately differ from some of our brother naturalists. 

 Goniodoris nodosa is to be found between tide-marks on the Northumberland coast nearly 

 the whole year round, but is most plentiful in the months of April and May, at which time 

 it is in the height of the spawning season. Large full-grown specimens may then be found 

 in the crevices of the rocks and under large flat stones, congregated together in considerable 

 numbers ; so many as forty or fifty specimens have been found under the same stone. At 

 this season the tints of colour are rather brighter than usual, particularly the blue patch on the 

 right side, which is produced by that curious organ, called the purple bag by Swammerdam, 

 appearing through the transparent skin. They are at this time generally distended with 

 spawn, which stretches the skin so as to entirely obliterate the tubercular elevations on its 

 surface. In this state we take it to be the Doris Barvicensis of Dr. Johnston. It is not 

 uncommon, however, to find large specimens at this season with the tubercles large and 

 conspicuous. At the commencement of the breeding season the tubercles are in all stages 

 of development, from the most perfect down to entire obliteration, when their white apices 

 alone mark their situation. After spawning most of the large individuals disappear, and the 

 species is scarce on the coast for a while until the young animals begin to make their 

 appearance, which they do in August. These are sometimes without tubercles in their 

 earliest stage, and the skin so thin as to allow the liver to impart a pink or brownish colour 

 to the back. This state exactly resembles the G. emarginata of Forbes. They soon 

 assume the form of Boris nodosa, Mont., which they retain through the remainder of the 

 season, though they continue to grow for some months afterwards. We have some suspicion 

 that the Doris marginata of Montagu may be another variety of this species, but if so the 

 figure is incorrect, as the foot is not seen beyond the cloak. Goniodoris elongata, Thomp., 

 we also place, not without hesitation, as another variety : one reason for doing so is, that 

 we collected many specimens of G. nodosa at Malahide (a locality near to that where 

 G. elongata was obtained,) which assumed, especially when contracted in spirits, much of 

 the elongated form of the latter animal. 



