180 Méscellaneous. 
dated eggs are always few in number. Nevertheless they arrive at 
the blastula stage, or sometimes the gastrula with a shallow invagi- 
nation. j 
Strongylocentrotus g and Spherechinus 9 .—The larve do not 
pass the blastula stage. 
Id. and Psammechinus 9 .—Plutei normally and perfectly deve- 
loped. ; 
Id. and Spatangus 2 .—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 eavity and caleareous 
spicules on each side of the mouth. 
Psammechinus 2 and Spherechinus g.—The larve always 
stopped at the gastrula stage, with the gastric invagination not deep. 
Id. and Dorocidaris G.—No uppearance of segmentation. (The 
same observation applies to both Dorocidaris and Strongylocentrotus.) 
Id. and Spatangus g .-—A few ova were segmented and attained 
the blastula stage. 
Psammechinus § and Spatangus 9 .—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 larvee are still in the gastrula state when the larve, 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 bemg much 
less abundant in the gastrule produced by crossed fecundations. 
Psammechinus § and Spherechinus 9 —A small number of ova 
beeome segmented, but do not pass the blastula stage. 
Crossed fecundations therefore are possible between different 
species of Eehinoidea, and that between very wide limits, There is 
certainly at least as much difference between a Spatangus and a 
Psammechinus as between two mammals belonging to two allied 
orders. And if the Plutei obtained by erossing 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 Psammechinus. 
I must, in conclusion, call attention to one fact :—Beecause 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 Psammechinus ; 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 Rev. Dr. H. C. McCoox. 
The author had observed that some of the orb-weaving spiders 
have a marked tendency to vary the forms of their nests. The 
