June 6, 1919] 



SCIENCE 



547 



bear. Four kinds of ground sloths have been ob- 

 tained in Cuba and one in Porto Rico; all are re- 

 lated to the large eitinct North American ground 

 sloth Mcgaloni/x. There are also several kinds of 

 rodents, all of them distantly related to South 

 American groups, chinchillas, spiny rats and per- 

 haps agoutis, and a very remarkable little insecti- 

 vore which is in a family by itself, and is found 

 both in Porto Rico and Cuba. A giant tortoise, 

 very thin-shelled like the tortoises of other oceanic 

 islands but in some respects very peculiar, a terra- 

 pin which stiU lives on the islands and is closely 

 related to species of the southeastern United 

 States, and a crocodile also still living and near to 

 a Central American species, are the principal fossil 

 reptiles. Although the collections are large, no 

 trace of any kinds of hoofed animals or carnivora 

 have been found, nor any other kinds of rodents 

 save the above South American groups, or of eden- 

 tates except the one famUy of ground sloths. The 

 characters of the fauna are believed to prove that 

 the islands have been isolated for a long time, at 

 least since the early Pliocene, and have never had 

 any direct connection with North America; and to 

 indicate that they have probably never had any 

 land connection with South or Central America. 

 There is little question that during the Pliocene or 

 Pleistocene the islands were elevated to or near 

 the borders of their submarine shelves, enlarging 

 and connecting them to some extent, and there is 

 some evidence, but not conclusive, for union of the 

 greater Antilles and as far east as the Anguilla 

 bank. 



Characters and restoration of the Sauropod genus 

 Ccemarasaurus Cope, from the type-material in the 

 Cope collection of the American Museum of 

 Natural History: Henry Fairfield Osborn, re- 

 search professor of zoology, Columbia University, 

 and Charles C. Mook. 

 Energy conception of the cause of evolution: 



Henry Fairfield Osborn. 

 The parasitic Aculeata, a study in evolution (illus- 

 trated) : William M. Wheeler, professor of eco- 

 nomic entomology, Buseey Institution, Harvard 

 University. 

 Two recent entomological problems — tlie pink boll- 

 worm and the European corn borer: L. O. 

 How.vKD, chief of Bureau of Entomology, U. S. 

 Dept. of Agriculture, Washington. 

 Hydration and growth: D. T. MacDouoal, di- 

 rector of the department of botanical research, 

 Carnegie Institution of Washington, Tucson, 

 Arizona. 



Hydration of agar and agar-protcin in propionic 

 acid and its amino-compounds : D. T. Mac- 

 DouGAL, director of the Desert Laboratory, Tuc- 

 son, Arizona, and H. A. Spoehr. 

 Sterility and self-and-cross-incompatability in shep- 

 herd's purse (illustrated): George H. Shull, 

 professor of botany and genetics, Princeton Uni- 

 versity. 



Sexual reproduction is a complex succession of 

 processes, all of which must be coordinated with a 

 considerable degree of perfection in order to be 

 successful. The chain of events leading from the 

 spore mother-cells (oogonia, spermatogonia) 

 through successful fertilization to fully developed 

 viable seeds, may be broken at any one of a num- 

 ber of different points, and may be affected by 

 many agents, both enrironmental and hereditary. 

 No one should expect, therefore, to be able to 

 bring all cases of sterility under a common view- 

 point. In the common shepherd's purse {Bursa 

 Bursa-pastoris) there exists a great number of 

 biotypes, each of which has its own characteristics 

 with respect to sterility and fertility, as well as 

 other features, both morphological and physiolog- 

 ical. In most of the common forms growing in 

 Europe and eastern North America the lower flow- 

 ers of the main axis are nearly always entirely 

 sterile. A species common throughout the Pacific 

 coast region of North and South America, and ex- 

 tending at least as far eastward as Tucson, Ari- 

 zona, has, on the other hand, no sterile flowers at 

 the base of the central raceme. A form similar to 

 the Pacific coast form has also been found in Hol- 

 land. A cross between the Tucson plants and those 

 from eastern America has given rise to partially 

 sterile hybrids which are characterized by 

 rhythmic succession of sterile and fertile flowers, 

 and there is some evidence that this rhythmic ar- 

 rangement is under the control of two genetic fac- 

 tors, so that the F. from such a cross consists of 

 about one like either parent to fourteen which dis- 

 play again a rhythmic succession of sterile and 

 fertile flowers. 



The basis of sex inheritance in Spharocarpos (il- 

 lustrated) : Charles E. Allen, professor of 

 botany, University of Wisconsin. (Introduced 

 by Professor Bradley M. Davis.) 

 Hydrogen-ion concentration of nutrient solutions 

 in relation to the growth of seed plants: Benja- 

 min M. DuoOAB, research professor of plant 

 physiology, Missouri Botanical Garden, St. Louis. 

 (Introduced by Professor Bradley M. Davis.) 

 The relation of the diet to pellagra (illustrated) : 



