SCIENCE- GOSSIP. 



17 



creature appropriated by Ceragnte. Smith, how- 

 ever, who examined the tube of Say's species, 

 found it to be lined with cement, and covered 

 externally with minute pellets, apparently of the 

 animal's excrement, together with fragments of 

 algae, etc. ( H ) ; and it cannot be doubted that the 

 structure is, either wholly or in part, the work of 

 the Cera/put. In the case of Cerapus calamicola 

 (Cyrtophium calamicola) Giles has ascertained, 

 curiously enough, that the tube has a vegetable 

 foundation, being, in fact, a short piece of hollow 

 reed, probably trimmed by the animal, and certainly 

 coated, both inside and out, with secreted matter, 

 doubtless laid down in the form of tine threads. 

 In some few of these tubes there was no trace of a 

 vegetable foundation, and it thus appears that 

 the creature is capable of constructing a tube 

 wholly of its secretion. 



The spinning-organs of these animals do not 

 appear to have been known until comparatively 

 recent years. Say — who, as we have just seen, did 

 not believe his Cerapus to be the maker of its 

 tube— remarked that it had no organ adapted to 

 this task. Bate and Westwood stated, of Am- 

 pTiitJtoe, that they had not been able to discover 

 whether the threads were excreted by the mouth, 

 or whether there was a special organ for their 

 production. The honour of discovering the 

 spinning glands belongs, I believe, to Smith ; 

 and one learns with surprise that he found them 

 in certain of the creatures' legs. They are not in 

 the first two pairs, the arm-like hand-bearing 

 gnathopods, but in the two pairs which follow — 

 namely, the first and second peraeopods, which are 

 the third and fourth pairs of thoracic limbs ; and 

 it is at or near the tip of the toe of these limbs 

 that the orifice is from which the thread issues. 

 While examining spirit specimens of Xenoelea 

 Smith noticed the opaque glandular structure of 

 the spinning apparatus, filling a large portion of 

 the two pairs of legs named — which legs, he says, 

 in most, if not all, of the non-tube-building Amphi- 

 pods are wholly occupied by muscles. A further 

 examination of the spinning legs of Xenoelea showed 

 that the terminal segment (dactylus) was not acute 

 and claw-like, but truncated at the tip, and appa- 

 rently tubular. Large cylindrical portions of the 

 gland were found to lie along each side of the basal 

 segment, and these two portion suniting at the distal 

 end of that segment, the gland passes through the 

 ischial and along the posterior side of the meral 

 and carpal segments, and doubtless connects with 

 the tubular dactylus. Similar structures were found 

 in the corresponding limbs in AinjpMtlioe macnlata, 

 etc. (") ; and also in Say's Cera2>us, in which the 

 basal segments of the spinning legs are very large 

 and almost wholly occupied by the glands ( l0 ). 

 (8) Smith, I.e. pp. 271-277. 



('•>) Smith, " Trans. Connecticut Academy," iii. (1874), pp. 32- 

 35; "Silliman's Journal" (3), vii. (1874), p. Gill; and "Ann. 

 and Mag. of Nat. Hist." (4), xiv. (1874), p. 240. 

 (10) Smith, 1882, I.e. p. 271. 



The subject has also received attention from 

 Nebeski. who detected the glands in the first ami 

 second peraeopods ; as a rule in the basos, the 

 ischium, the meros, and the carpus, from whence 

 ducts let out the secretion ,it the tip of the toe r 

 with results happily identical with those of Smith. 

 The apparatus occurred in all the Corophiidae 

 examined by Nebeski — namely, species of Micro- 

 detitopu8, Microprotopux, Amjihithor, I'odocerus, 

 Cerapus, and Corophiim, the secretion being used, 

 without doubt, for cementing and plastering as 

 well as for spinning ("). Giles, writing of Cerwpui 

 calamicola, doubtfully supposed the spinning 

 glands to be in the huge propodal segment of the 

 second gnathopods ; but this suggestion, probably 

 erroneous, was not made in opposition to the find- 

 ings of Smith and Nebeski, with whose writings 

 Giles was doubtless unacquainted. 



Smith, fortunately, has seen the creatures in the 

 act of spinning their threads. In 1874 he watched 

 the construction of the tube in several Amphipods, 

 including a species of Amphitho'e ; and has given 

 an interesting description of the proceedings of 

 Microdentqpus gryllotal/pa {M. gra/ndimam/us) — a 

 particularly favourable subject for observation. 

 When placed in a zoophyte-trough with small 

 branching algae, this Amphipod generally com- 

 menced at once to construct a tube, and it could 

 readily be observed under the microscope. A few 

 slender branches of the alga were pulled towards 

 each other by the antennae and gnathopods, and 

 fastened by threads of cement spun from branch 

 to branch by the spinning limbs above mentioned. 

 The branches were not usually at once brought 

 near enough together to serve as the framework 

 of the tube, but were gradually brought together 

 by being pulled in and fastened a little at a time, 

 until at last they were brought into the proper posi- 

 tion, where they were then firmly held by means of 

 a thick network of fine threads of cement spun 

 from branch to branch. After the tube had assumed 

 very nearly its complete form, it was still usually 

 nothing more than a transparent network of 

 cement threads woven among the branches of the 

 alga, though occasionally a branch of the alga 

 was bitten off and added to the framework. Very 

 soon, however, the animal began to work particles 

 of excrement and bits of alga into the net ; the 

 pellets of excreta, as passed, were taken in the 

 gnathopods, maxillipeds, &c, broken into minute 

 fragments, and worked through the web, upon the 

 outside of which they seemed to adhere partly by 

 the viscosity of the cement threads and partly by 

 the tangle of threads over them. Excreta and bits 

 of alga were thus worked into the wall of the tube 

 until the animal within was protected from view, 

 and, during the whole process, the spinning of 



(11 ) Nebeski, " Arb. Zool. Inst. Wien," iii. ( 1880), pp. 111-163, 

 as abstracted iiy Stebbing, torn. cit. pp. 518-521, 1155 ;" ZooL 

 Record," xviii. (1881), Crust., p. 6; "Journ. R. Micr. Soc." (2),. 

 i. (1881), pp. 453-455. 



