152 



SCIENCE 



[N. S. Vol. XXVI. No. 657 



pure-bred 0. LamarcTciana so far studied I 

 have found no indication of the number ever 

 approaching twenty; but from the evidence of 

 repeated counts it seems to be fourteen or 

 fifteen. I have at least eighteen good clear 

 demonstrations of mitotic figures showing only 

 fourteen chromosomes, all distinctly outlined 

 and clearly defined — with no trace of a chro- 

 mosome in a preceding or following section; 

 on the other hand, I have encountered a suffi- 

 cient number of less clearly defined figures, 

 in which there seems to be but thirteen, and 

 in others fifteen chromosomes, to make it 

 necessary to state the number for the present 

 with reserve. Chromosomes frequently lie in 

 such positions as to make it impossible to dis- 

 tinguish between a long-looped form and two 

 so placed as to give a similar appearance; also 

 a looped chromosome may be sectioned at a 

 point to give the two halves the appearance 

 of distinct individuals. 



The number of chromosomes characteristic 

 of the somatic cells of 0. gigas is probably 

 twenty-eight or twenty-nine, although the diffi- 

 culty in counting is here increased by the 

 large number; however, I have six or seven 

 excellent figures showing twenty-eight sharply- 

 defined chromosomes, and as many more, not 

 so clearly outlined, in which there is a strong 

 indication of twenty-nine. It is hoped that 

 the hundreds of new sections now in process 

 of preparation for study will establish the 

 facts, shortly. 



Other points of interest are coming to light, 

 particularly in connection with the hybridiza- 

 tion of mutants, and will be mentioned in a 

 later note. ^^^^^ ]y;_ ^utz 



Station fob Experimental Evolution, 

 Cold Speing Harbor, L. I., 

 June 28, 1907 



CURRENT NOTES ON LAND FORMS 

 diamond head and mohokea 

 0. H. Hitchcock has recently described a 

 tuff cone and a caldera in the Hawaiian 

 Islands (" Geology of Diamond Head, Oahu," 

 Bull. G. 8. A., XVIL, 1906, 469-484; 

 "Mohokea Caldera," ihid., 485-496). Dia- 

 mond Head, on the island of Oahu, is a well- 



formed tufl: cone with a broad and shallow 

 crater, which the author concludes was thrown 

 up explosively from beneath the level of the 

 sea, the volcanic material having been ejected 

 through fossiliferous limestones of Tertiary 

 age. The cone is compared with the Monte 

 Nuovo near Naples. Considerable attention is 

 given the conflicting theory that the cone was 

 built up gradually by the slow accumulation 

 of material ejected at long intervals. The 

 features of the cone are illustrated by several 

 plates. 



Mohokea, on the island of Hawaii, is de- 

 scribed as a very irregular caldera only 

 partially enclosed, the open, side being toward 

 the sea. Two parallel lines of faulted and 

 tilted lava blocks cross the caldera from 

 southeast to northwest, and are believed to be 

 part of the overlying crust which dropped in 

 when the caldera was formed, although the 

 blocks themselves have been in part crowded 

 up until their crests rise higher than the 

 surface without the caldera. Mohokea is com- 

 pared with the irregular Haleakala caldera, 

 and illustrations of both are given. 



D. W. J. 



A PENEPLAIN IN EQUATORIAL AFRICA 



It is generally accepted among physiog- 

 raphers that a peneplain worn down on crystal- 

 line rocks in a humid climate would be 

 heavily cloaked with a deep soil of local 

 weathering; and in favor of this opinion the 

 deeply decayed rocks of the somewhat up-' 

 lifted and dissected Appalachian Piedmont 

 belt may be instanced. In a subarid climate 

 the case is different. 



An excellent account of an extensive pene- 

 plain, exposing large areas of bare rock, on the 

 southern border of the French Sahara in lati- 

 tude 18° to 21° N., northeast of the great bend 

 of the Niger and on the arid outer border of 

 the subequatorial (summer) rains, is given 

 by E. F. Gautier (" A travers le Sahara 

 frangais," La Geogr., XV., 1907, 1-28). The 

 rocks of the region are for the most part 

 Archean granites and gneisses, broken here and 

 there by less ancient igneous intrusions, and 

 associated with belts of strongly folded and 



