1899] CURRENT LITERATURE 147 
seems most extraordinary and unlikely action of the second sperm will be 
awaited with interest.— Since the foregoing was in type, a preliminary paper 
has been published by Nawaschin’ in which few other important facts are 
added. The copulation with the polar nucleus is considered as a sexual act, 
so that “we have to do here with a sort of polyembryony which issues in the 
formation of a pair of unequally developed twins, of which one- develops 
into a segmented plant, while the other remains thallus-like and is finally 
consumed by the former.’’—C. R. B 
Mr. CuarLEs E, Brooks has recently discussed ® the origin. and signif- 
icance of spines, both in animals and plants. He endeavored to arrive at 
general conclusions relating to the origin and significance of spinosity. The 
main part of the paper is devoted to conclusions derived from the study of 
both living and fossil animals. The observations made on plants are some- 
what superficial ; the same general conclusions, however, are obtained in both 
plants and animals, These are that spines, whether prickles, thorns, or 
horns, represent “a stage of evolution, a degree of differentiation in the 
organism, a ratio of its adaptability to the environment, a result of selective 
forces, and a measure of vital power.” = 
kj ae a preliminary discussion on the law of variation, the growth and 
= a the ontogeny of the spinose individual, and the phylogeny 
; *orms, the author classifies the causes of spines under eleven cate- 
: aes ante unimportant exceptions the spines of plants are referable 
suppression ss these, he first is the “restraint of environment causing 
May be sy or structures, ie desert or arid regions leaves and branches 
Ppressed to form spines, A secondary influence may determine 
ants in a region. Herbivorous animals destroy 
and an old pasture may thus have the prevailing flora 
€tazing animals. This does not produce spines, but merely 
ll species except those the animal cannot eat; hence the spines 
uced ‘by Suppression of stipules, leaves, etc. The cause of these corti- 
ady rthe author admits, is not clear, but he seems to favor the idea 
the ey are connected with the general suppression of 
and that they represent abortive attempts on the part of the 
nder cat : , but this is not the initial cause. 
7B “Sones of interpretation the author offers two generalizations. 
wil, : 
*Am. a Imp. Sci. St. Pétersb. 7: 377-382.- 18098. 
é - Sci. IV. 6: 1-20, 125-136, 249-268, 329-359. 1898. 
