180 Miscellaneous. dated eggs are always few in number. Nevertheless they arrive at the blastula stage, or sometimes the gastrula with a shallow invagi-nation. StrongyJocentrotus J and Sphaireehinus § . — The larvae do not pass the blastula stage. Id. and Psammeehinus 5 • — Plutei normally and perfectly deve-loped. Id. and Spatangus $ . — All the ova become regularly segmented. I have never seen them attain the Pluteus stage ; they do not pass the stage of perfect gastrula, with a gastric cavity and calcareous spicules on each side of the mouth. Psammeehinus $ and SpJicereehinus tf . — The larvae always stopped at the gastrula stage, with the gastric invagination not deep. Id. and Dorocidaris <$ . — No appearance of segmentation. (The same observation applies to both Dorocidaris and Strongylocentrotus.) Id. and Spatangus 3 • — A few ova were segmented and attained the blastula stage. Psammeehinus S an( i Spatangus $ . — In all the experiments all the ova attained the stage of Plutei, and these lived for several days. The development takes place comparatively very slowly ; thus, the hybrid larvae are still in the gastrula state when the larvae, obtained by direct fecundation under the same conditions, have attained the Pluteus stage a day or two. Moreover the form of the Pluteus presents some peculiarities ; the arms are shorter and stouter, and the contours are less regular than in the normal Plutei of Spatangus ; the calcareous skeleton also presents differences. Even in the gas-trula we observe peculiar characters, the pigmentation being much less abundant in the gastrulae produced by crossed fecundations. Psammeehinus 3 and Sphwrechinus § . — A small number of ova become segmented, but do not pass the blastula stage. Crossed fecundations therefore are possible between different species of Echinoidea, and that between very wide limits. There is certainly at least as much difference between a Spatangus and a Psammeehinus as between two mammals belonging to two allied orders. And if the Plutei obtained by crossing between regular Echinoids do not appear to differ much from the legitimate Plutei of the type functioning as female in the experiments, there are cer-tainly well marked differences between a legitimate Pluteus of Spatangus and a hybrid Pluteus of Spatangus and Psammeehinus. I must, in conclusion, call attention to one fact : — Because the ova of a species when fecundated by the spermatozoids of another species arrive at the state of Pluteus, it does not follow that the converse is true. Thus the ovules of Spatangus are perfectly fecundated by the spermatozoids of Psammeehinus ; but the ovules of the latter, sub-jected to the influence of the semen of Spatangus, remain for the most part intact, while the rest scarcely reach the blastula stage. — Comptes Rendus, April 24, 1882, p. 1203. On Variation in the Nest-forms of the Furrow-Spider (Epeira strix). By the Bev. Dr. H. C. McCook. The author had observed that some of the orb-weaving spiders have a marked tendency to vary the forms of their nests. The
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