202 



NATURE 



[June 26, 1890 



II. February 21, 1890. [Large supply of Ancula cris- 



tata, and a few Dendronotus arborescens, Eolis rufi- 



branchialis^ and Eolis picta from Hilbre Island.] 



Mr. Moore and I each ate an \Ancula. The specimen 



was placed alive upon the tongue. No stinging or other 



disagreeable sensation was perceived. It was then 



chewed slowly and swallowed. The taste was pleasant, 



and distinctly like that of an oyster. 



Tank K.— Ancula. 

 (i) Seized and rejected by a shanny, and then bolted 

 suddenly by a second. 



(2) Seized and rejected by ten fish in rapid succession. 



(3) Seized, when falling, and swallowed by a fish. 



(4) Seized and rapidly rejected by five fish in suc- 

 cession. 



(5) Seized and rapidly rejected by four fish in suc- 

 cession. 



Tank V^.—Anada. 

 (i) Seized and rejected by a young cod and six plaice 

 in rapid succession. 



(2) Seized and rejected by seven plaice, and left lying 

 on sand. 



(3) Seized and rejected by four plaice, and left lying on 

 sand. 



The fish were then tried with some cockles, which, 

 when thrown in, were eagerly pounced upon and eaten. 



(4) Then four specimens of Ancula were dropped in 

 together, and were tried and rejected by two young cod 

 and three plaice. 



Tank Q.— Ancula. 

 (i) Touched by a young cod, but not taken, then tried 

 and rejected by goldsinny. 



(2) Touched and rejected several times by young cod. 



(3) Touched and rejected by first cod, bolted suddenly 

 by second. 



The shannies at once take an object into the mouth, 

 even though they reject it again immediately, but the 

 young cod usually approach it very closely, and appaar to 

 smell it or feel it with the lips, and then turn away from 

 it, or else suddenly bolt it, in which case it does not re- 

 appear. The shanny seems to test the edibility inside its 

 mouth, the cod outside. 



Some crabs {Hyas araneus) in two small tanks were 

 then tried with specimens of Ancula with the following 

 results : — 



(i) Seized at once by crab, but eaten very slowly, and 

 only partially. 



(2) Taken no notice of. 



(3) Taken up with chela, then dropped and left. 



(4) Apparently not noticed by crabs. 



The three last specimens of Aitcula were found alive 

 and fully expanded next day, and crawled about the two 

 crab tanks undisturbed for some time afterwards. 



Finally, a few specimens of Ancula were offered to two 

 large anemones {Actmoloba), but were not taken. 



In all, then, Ancula was rejected by 53 animals and 

 taken by four. These experiments gave us the distinct 

 impression that Ancula was distasteful to the animals 

 tried, although we did not at that time understand why, 

 and had expected to get a contrary result. 



Tank A. — Dendronotus. 



(i) Seized at once by shanny, and carried off to back of 

 tank ; shortly afterwards two shannies were found fighting 

 over it, each having hold of an end, as they do with a 

 large worm ; finally, they each ate a part of the Dendro- 

 notus. 



Tank B. — Dendronotus. 



(2) Tried and rejected by brill and young cod. Then 

 seized by plaice and kept in mouth for a long time (five to 

 ten minutes), during which it was pursued by other fish. 



NO. 1078, VOL. 42] 



Tank C. — Dendronotus. 



(3) Touched and left by young cod ; taken partly into 

 mouth and rejected by two bullheads four or five times. 



The general impression we received was that Dendro- 

 notus was more acceptable to the fish than Ancula, but 

 that they were incommoded by the size. Our specimens 

 were large ones— over two inches in length— and none of 

 the fishes tried seemed able to get the whole of the Den- 

 dronotus comfortably into the mouth, at once. Several 

 took half the body into the mouth, and swam about with 

 the other half hanging out. This was well seen in the 

 case of the two shannies, who each ate half of the specimen, 

 and of the plaice which carried about its prey for a con- 

 siderable time, during which it was actively pursued by the 

 others. That specimen was in all probability eaten by one 

 or more of the plaice, as we could not find any trace of 

 it a short time afterwards. The rejection by the bull- 

 heads may be accounted for by the awkward size of the 

 morsel. The two fish had each at least two tries at it, 

 taking it half into the mouth, giving it a shake, sending it 

 out, and then going at it again as if to get a better hold. 



Tank A.— Eolis. 



(i) Seized by largest shanny, who at once shook it 

 vigorously, and kept moving its jaws and ejecting the 

 cerata 1 in groups of three or four, and finally put out the 

 rest of the body. Then tried and rejected by four or five 

 other fish in rapid succession, and then by the large 

 shanny again, then by several others, and finally left lying 

 on the bottom. The large shanny who first tried it was 

 going about for some time afterwards with the mouth held 

 open. 



Tank C— Eolis. 



(2) Touched or tried, and rejected at once by cod, bull- 

 head, and weever. The cod came very near it, or touched 

 it with its snout, several times afterwards, but never look 

 it into the mouth. 



Eolis is undoubtedly distasteful. The cnida (sting- 

 ing cells) on the tips of the cerata probably sting 

 the lips of the fish. As it had occurred to me that 

 the natural conditions would be more nearly reproduced 

 if the Nudibranchs were not dropped into the tanks, on 

 the following day, February 22, a few specimens of Ancula 

 were placed upon pieces of stone and lowered cautiously 

 into tanks A and B in such a way as not to attract the at- 

 tention of the fish. The Nudibranchs reached the rock- 

 work safely, and were seen crawling over various parts of 

 the tanks for several days untouched by the fish (shannies 

 and flat-fish). Woods, the aquarium attendant, tells me 

 that the fish sometimes went up close to the Ancula, 

 and looked at them, but never attempted to touch 

 them. The Nudibranchs were last seen about a week 

 after being put into the tanks. They then disappeared, 

 but may possibly have retreated into the back part of the 

 tank, or have crawled up out of the water, as Ancula is 

 very liable to do when kept in captivity. 



III. March 22, 1890. {Dendronotus, Eolis, and Doris 

 from Hilbre Island.] 



Tank h.— Dendronotus. 



(i ) Seized at once by the large shanny and kept in the 

 mouth, half the Nudibranch projecting. This shanny 

 was pursued by others, one of which caught the projecting 

 end of the prey, and in the ensuing struggle tore half the 

 body off and ate it. The large shanny at once retreated 

 with the remainder to the back of the tank, came out 

 shortly afterwards with the Dendronotus still in mouth, 

 and was again pursued and retreated to the dark, appear- 

 ing again soon without the Nudibranch. 



' The coloured dorsal paj illas which contain the stinging cells. 



