July 3, 1885." 



SCIENCE. 



be published in the first number of the pro- 

 ceedings of the societ}', which will appear during 

 the summer. Besides these set experiments, 

 Mr. W. H. Pickering of Boston met with some 

 success in the experiments which have attracted 

 so much attention from the English society, — 

 experiments in which a drawing thought of 

 by one person, is reproduced by another, who 

 has no visible means of obtaining information 

 as to what the drawing may be. In the ac- 

 companjing illustration we have reproduced 

 all the figures as they were drawn, numbering 

 them from 1 to 52. The upper line in each case 

 contains the originals, and the lower the re- 

 productions. The originals were made either 

 by Mr. Pickering or by one of his friends, and 

 the reproductions were most of them made 

 by a young lady, w^ho, on one or two evenings 

 when the experiments were tried, met with 

 some success. It may be well to state, that 

 with figs. 6, 7, 8, and 20, certain extraneous 

 causes acted which interfered with the results. 

 The first forty figures were all made in one 

 day ; figs. 41 to 47 inclusive were made by 

 another person ; the remaining figures were 

 made by the sensitive, so called, on a day when 

 apparenth^ there was no thought-transference. 



MIMICRY AMONG MARINE MOLLUSCA. 



It is a curious fact, that, while among the 

 terrestrial animals the number of known cases 

 of protective mimicry is ver}' large, among 

 aquatic animals it is verj' small. I have no doubt 

 that the comparative poverty of our knowl- 

 edge of the habits and situation of aquatic 

 animals in part accounts for this, but I believe 

 also that there is really vastly less mimicking. 

 I do not know of any marine species, that, 

 harmless in themselves,' mimic formidable spe- 

 cies for protection ; but there are instances in 

 which forms are modified in color or shape so 

 as to resemble the surroundings in which the}^ 

 live, and thus escape the observation of their 

 enemies. In the summer of 1879, Dr. E. B. 

 Wilson, while studying in Brooks's laboratory 

 at Beaufort, N.C., found abundant specimens 

 of Ovulum uniplicatum, — a mollusk living 

 upon the stems of Leptogorgia virgulata (a 

 sea-fan abundant there in shallow sounds). 

 The stem of the sea-fan is of an orange-3^ellow 

 color, and, further, is often marked with yellow 

 swellings where the coral has spread itself over 

 the shell of an attached barnacle. The Ovulum 

 has a 3'ellow shell ; and the skin folds up over 

 the shell, and is also of an orange-yellow color, 

 — precisely the same color as that of the pen- 



natulid, — so that the snail escapes notice very 

 readily indeed. It is abundanth' found upon 

 the Leptogorgia, and never met with except 

 associated with it.^ Last summer at Beaufort, 

 in trawling in ten fathoms of water, a few 

 miles oflE* Cape Lookout, we took a Leptogorgia 

 whose general habit was the same as that of 

 L. virgulata, but which was ver}' different from 

 it in color. In this one the color is deep rose, 

 almost purple, and mottled with white at the 

 openings, where the polyps are fixed. Xow, 

 the question was, Is there an Ovulum for this 

 Leptogorgia ? and on examination, sure enough, 

 there was found a large number of the Ovu- 

 lums, in this case again imitating the colors of 

 the host. This Ovulum is undoubtedly of the 

 same species as the yellow one, for it presents 

 no difference except in color. The shell is red- 

 brown ; and the folds of skin that surround it 

 in the expanded snail are deep-rose color, and 

 mottled with white spots. Here, then, is an- 

 other very good illustration of the familiar 

 principle that forms will var}^ in adaptation to 

 their surroundings, and of the part that mim- 

 icry may play in natural selection. Confined 

 in aquaria, the snails sought their own corals 

 to creep over them ; and, if the red snail and 

 yellow coral only were put into the same aqua- 

 rium, the snail showed not the least desire to 

 creep over the coral, but remained creeping 

 about the walls of the aquarium. 



I observed another snail last summer that I 

 feel sure must owe its shape and color, at least 

 in part, to mimicr3% though here there were not 

 so good grounds for the conviction as in the 

 case just mentioned. I found on the beach at 

 Fort Macon, one day after a strong southerly 

 gale, a single specimen of an undetermined spe- 

 cies of Scyllaea, — a nudibranch characterized 

 b}^ a pair of tentacle shields, and two pairs of 

 elongate narrow processes of the skin upon the 

 back, on the inner side of which white delicate 

 gills are placed. This creature, when placed 

 upon the Sargassum, or gulf- weed, shows the 

 closest resemblance to it. The color is almost 

 identical with that of the alga, a light brown. 

 The body is elongate and much compressed, 

 and the foot-sole an elongate, narrow groove, 

 perfectl}^ adapted for adhering to the alga stem. 

 The tentacle sheaths and the skin processes 

 upon the back are thin, and at the edges are 

 w^avy, and present the most perfect resem- 

 blance to the leaves ( ?) of the alga. The 

 compressed body is further terminated poste- 

 riorly b}^ a thin vertical portion like a fin, 



1 Dr. W. Breitenbach, in Popular scie?ice moiithh/, January, 

 1885, p. 365, mentions vaguely some nudibranch that imitates the 

 sea anemones upon the stems of Sargassum. 



