490 



NATURE 



{March 27, 1890 



Foreign Substances attached to Crabs, 



Since Hyas is one of the most abundant Crustaceans found 

 off the east coast of Scotland, Mr. Holt must adduce consider- 

 ably more than two instances before it can be admitted that the 

 attachment of Simple Ascidians to this crab is at all a usual 

 occurrence. Tf it is, I should still be anxious to inquire whether 

 the crab does not — in spite of the apparent difficulty of the 

 operation — place the Ascidians upon its back with its own nip- 

 pers. I may cite Gosse's well-known experiment with Pagurus 

 pn'deauxii and Adamsia palliata, described in his "Year at 

 the Shore," for the purpose of analogy. But Mr. Holt will 

 find a case, probably quite similar to that which he mentions, in 

 Bell's "Stalk-eyed Crustacea." Two specimens of Hyas ara- 

 neus were found with oysters attached to their backs, that on the 

 larger crab being three inches in length, and five or six years 

 old, probably a much more "serious incubus " than Mr, Holt's 

 Tunicates. The crab's carapace was but two and a quarter 

 inches in length. Hence, despite the "world of weight upon 

 its shoulders, ' Mr, Thompson concluded that "the presence of 

 this oyster affords interesting evidence that the Hyas lived 

 several years after attaining its full growth," Probably the 

 larvae of the oysters, and of the Ascidians also, happened 

 to alight upon the crabs at the end of their free-swimming 

 existence, although six or seven years seems to me to be a 

 remarkably long age for a Hyas. 



Barnacles upon the backs of Maia, Carcinus, &c,, are also 

 due to the same, as it were, accidental cause. 



But, whatever the explanation, these exceptional cases do not 

 alter the fact that the foreign bodies found upon Hyas are usually 

 fixed there by the crab itself. The specimens I have seen have 

 been covered with fragments — not living colonies — of Algas, 

 Hydroids and Polyzoa, which are fastened by the hairs of the 

 crab's carapace and legs exactly as in Stenorhynchus, and in 

 this crab the process of attachment has been frequently observed 

 here and accurately recorded. 



At the same time I by no means hold that the two groups 

 which were defined in my previous letter are absolutely marked 

 off from one another. The hermit crabs make use of both 

 methods of protection. Bits of Sponges may frequently be seen 

 upon the carapace of Maia, Sienorhynchtis, and Inachus, and I 

 have occasionally found colonies of Leptoclinum and Didemnum 

 upon both Maia and Inachus. In these cases the inconspicuous 

 appearance is not lost, but the attachment of small Sponges and 

 Didemnids is probably an additional protection against the 

 numerous night-feeding fishes, which hunt their prey by the 

 senses of smell and touch. 



As to the inedibility of Tunicata, I did not — as Mr. Holt 

 states — "assume "it. I have experimentally found it to be a 

 fact (as I stated in my letter) that the odour and taste of " Tuni- 

 cata, and especially Compound Tunicata" are almost invariably 

 sufficient to prevent fishes from eating them. Exceptions do 

 not disprove the rule, and it is quite possible that Pelonaia is 

 not distasteful. But this is not established by a few specimens 

 having been taken on one or two occasions from the stomachs of 

 Cod, Haddock, and Dab ; and although Mr. Holt quotes Prof. 

 Mcintosh as speaking of the "abundant " occurrence oi Molgula 

 arenosa in the stomachs of Cod and Haddock, he will find upon 

 reading Prof. Mcintosh's words again, that they are open to a 

 different interpretation. 



In my previous letter I omitted to mention that a species of 

 hermit crab also, Eupagurus lucasii, takes advantage (regu- 

 larly?) of the distastefulness of Compound Ascidians. Mr. 

 Harmer has, with much kindness, examined for me a specimen 

 in the Cambridge Museum. The crab inhabits a univalve which 

 is covered with Distaplia magnilarva. 



Mr. Holt's statenient that '^^ Actinia mesenibryanthemum is 

 certainly a favourite food of the Cod " is so astonishing that I 

 hope he will adduce the evidence for his assertion. Mr. Brook 

 had not found this to be so when he reported upon the food of 

 this fish for the Scottish Fishery Board, and indeed only the 

 youngest Cod ever frequent the tidal' waters to which A. viesem- 

 bryanthet.um is confined. P'urther, although Paguiiis bej-n- 

 hardus, when not associated wiih an Anemone, is very frequently 

 found in the stomachs of Cod and Haddock, I do not know a 

 single instance of its having been found in the stomachs of the 

 same fish when associated with one. 



I am informed by Mr. Poulton that, in a work which is shortly 

 to appe?r, he has included such animals as Stenorhynchus and 

 Caddi- •orms, which disguise their appearance with foreign 

 bodie simply in order lo escape identification by enemies, in a 



group to which he gives the very convenient name " allo- 

 cryptic." Animals which trust rather to the offensive than to 

 the inconspicuous character of the foreign bodies with which 

 they associate themselves he terms "allosematic" (crTjyuo, a 

 sign)._ 



It is obvious that the allosematic method of protection is all 

 but perfect, since it is largely free from the loss due to experi- 

 mental tasting attendant upon the method of a purely warning 

 appearance ("autosematic"). Walter Garstang. 



Plymouth, March 21, 



Sea-bird Shooting. 



Is it not time that something more was done to stop the 

 wholesale slaughter of our sea-birds ? During the past winter 

 the havoc has been terrible, and unless some restraint is imposed 

 we may expect before long to find our shores denuded of their 

 white wings. When the birds had no value, there was a limit, 

 though a wide one, to their destruction, because of the 'cost of 

 killing them ; but recently a large demand has sprung up for 

 their skins, and an organized traffic is now carried on in the 

 carcases. 



The shooter gets from threepence to sixpence per bird from the 

 amateur dealer, and for the sake of this paltry sum (surely the 

 birds are worth more to us alive than this !) there is not a 

 sporting lounger on the coast who can possess himself of a gun 

 who does not kill every bird which can be reached either from 

 the shore or from a boat. The gulls are pursued, I am told, 

 even as far as the Dogger Bank. 



The beautiful kittiwake is the greatest sufferer. One of the 

 dealers boasted to me the other day that he had passed " nearer 

 ten than nine thousand dead birds through his hands this 

 season, chiefly kittiwakes," He added that he had got 804. 

 carcases in one batch from one sportsman. 



From inquiries, I judge that this person's trade represents 

 about one-third of the dead birds which have been sent away from 

 our little town this season. I know the traffic is carried on at 

 other points, and no doubt this is but an example of what is 

 going on all round our coast. When we consider that the car- 

 cases which can be secured represent only a fraction of the birds 

 killed or injured, we gain some idea of the extent of the mis- 

 chief. Indeed, during the past month it has been possible to 

 take a long walk along our shore without seeing a single sea- 

 gull. Who wishes to see a blank seascape ? 



Now, surely, we all have equal rights in these graceful birds, 

 and the numerous class who love to see them alive deserve 

 as much consideration as the mischievous minority whose plea- 

 sure it is to destroy them ! It is not as though these latter 

 were worthy persons, compelled \to a cruel employment for 

 their daily bread : they are, on the contrary, nearly all of a 

 class who deserve no sympathy — of a comfortable class who, 1 

 verily believe, would shoot their next-door neighbours if they 

 could do so with impunity, and could dispose of the carcases I 

 Just imagine the new variety of "sport" which one of them 

 described to me not long ago ! He said you could catch the 

 gulls at sea by baiting a floating fishing-line with liver, and in 

 this way, though you did not get quite so many as with a gun, 

 you had far better yi<«, especially from the kittiwakes, as they 

 are wonderfully "game," and, when they feel the hook, 

 " flacker about and scream like a child"! 



Is it too much to ask that our Legislature, which has spent so 

 much time in the past on laws in the interests of the' so-called 

 "preservers"of game, will do something, and that speedily, in the 

 interests of those who would fain be truly preservers of the sea- 

 birds ? At least they should extend the protection afforded to 

 " game" to these noiile birds, and order that those who shoot 

 them shall pay a heavy license for their despicable sport, and 

 those who deal in the dead carcases a still heavier. 



And nothing in this matter must be left to local authorities. 

 In seaside places self-interest vitiates the sentiment on this ques- 

 tion. The fisherman finds it easier t« earn money by letting his 

 boat to the " sportsman " than by his legitimate productive in- 

 dustry ; the tradesman fears to lose these men's custom ; and the 

 gentry, mostly supporters of "sport," are perhaps not sorry to 

 have such an excellent safety-valve for guns which might other- 

 wise poach on their preserves ; and besides, there is in Yorkshire 

 a semi-political aspect to the matter. Thus it has happened that 

 of late years the clause in the (so far as it goes) excellent '" Sea- 

 birds Preservation Act " of 1869, which permits a lengthening 

 of the close time under certain conditions, has been rendered 



