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SCIENCE 



[N. S. Vol. XXV. No. 649 



therefore, have been greater rainfall in the 

 past when erosion had not accomplished so 

 much of its leveling effect, and remarks that a 

 map of that old-time distribution of rainfall 

 is capable of construction on the basis of the 

 approximate land elevations of the land before 

 denudation took place. In this sense the de- 

 nudation of the land has been accompanied by 

 diminution of precipitation. It should be re- 

 membered, however, that regional uplift has 

 the opposite effect and has not infrequently 

 been the occasion of increase of rainfall and 

 denudation. The Black Hills of South Da- 

 kota, for instance, have more rainfall than the 

 region about because of the domed uplift of 

 the region above the plains. It is estimated 

 that 3,000 feet have been removed from their 

 summits by denudation since this uplift and 

 this' Kassner would suggest must have been 

 accompanied by diminution of rainfall. But 

 it is quite conceivable that the summits have 

 never been more than 700 feet above the 

 sea, for denudation has been lowering them 

 at the same time that doming has thrust 

 them up. In that case there has been no 

 reduction in height or diminution of rainfall. 

 When uplift ceases and denudation alone con- 

 trols the elevation, rainfall must undergo the 

 diminution spoken of, but the complete cycle 

 of changes began with increase of rain as the 

 doming first began. This supplied the abun- 

 dant transporting agent with which erosion 

 resisted further effective uplift and brought 

 increase of precipitation to a halt much as the 

 governor controls the throttle of an engine. 

 Prom what we may call a mature stage of 

 rainfall, reached likely enough in geographic 

 maturity of the mountain forms, Kassner's 

 diminution must come in. 



Mark S. W. Jefferson 



Ypsilanti, Mich. 



SPECIAL ARTICLES 



THE DEVELOPMENT OF UNFERTILIZED FROG EGGS 

 INJECTED WITH BLOOD 



During three successive springs (1905-7) the 

 writer has experimented on unfertilized frog 

 eggs by injecting them with blood or lymph 



of either male or female frogs. In all some 

 fifteen hundred eggs have been so operated 

 upon. Shortly before the time for laying, the 

 eggs were taken from the uterus with every 

 precaution to prevent contamination by sperm. 

 Those nearest the cloacal opening were always 

 set aside as a control and in not a single 

 instance did any of them develop. The other 

 eggs were pricked with a very fine-pointed 

 capillary tube which had previously been 

 charged with lymph and corpuscles by dipping 

 it into the lymph or the blood of another frog. 



In eggs so treated numerous instances of 

 cell proliferation and embryonic development 

 have been observed, provided the eggs were 

 fully matured and ready for fertilization. 

 Many eggs after six or eight days showed 

 upon sectioning that they had approximated 

 the full blastular and in some cases the gas- 

 trular stages, although the condition came 

 about apparently by some sort of internal 

 nuclear arrangement, as no superficial cleavage 

 furrows were observable and no demarcation 

 into cells was visible from the exterior until 

 the third or fourth day, when close inspection 

 showed in some cases numerous small vesicu- 

 lar or cellular outlines. 



In some instances definite organs were de- 

 veloped, though frequently distorted and mis- 

 placed. Cross-sections of one embryo, for ex- 

 ample, showed such pronounced defects as two 

 neural tubes anteriorly. Of the whole num- 

 ber of eggs operated upon only two developed 

 into free-swimming tadpoles and these were 

 apparently normal as far as superficial exam- 

 ination disclosed. They have not yet been 

 sectioned. After sixteen days one died and 

 the other was killed to insure proper fixation 

 for histological study. 



Apparently the white rather than the red 

 corpuscles are the stimulating agents which 

 bring about development, because injections 

 of lymph, which contains only white cor- 

 puscles, produce the same effect as injections 

 of blood. Whether or not the fluid part of 

 the lymph or blood produced any effect could 

 not be definitely determined from the material 

 at hand. The whole effect seems, however, to 

 be the result of the proliferation of the leuco- 



