May 14, 1915] 



SCIENCE 



715 



I am inclined to see another confirmation 

 of this interpretation in a well-known ob- 

 servation of Morgan on the regeneration of 

 Planarians. He found that if a piece be 

 cut from the body at right angles to the 

 longitudinal axis the head will form along 

 the whole cut edge of the piece, while if a 

 piece be cut out obliquely a tiny head will 

 form in the foremost corner of the cut edge. 

 As Bardeen suggested, this would find its 

 explanation on the assumption that the head 

 formation is induced by the collection of 

 certain material which will collect along the 

 whole front when the piece is cut out of the 

 body at right angles, while it is bound to 

 collect in the foremost angle when the piece 

 is cut out obliquely. 



"When we summarize all the facts we may 

 state that it may be inherent in each cell 

 to grow and divide eternally under suitable 

 conditions; and that we can understand 

 this condition on the simple assumption of 

 the existence of synthetic ferments or syn- 

 thetic mechanisms in each cell which are 

 formed from the food taken up by the cells. 

 In reality, however, things do not happen 

 in this way in multicellular organisms, and 

 not even in their egg cells. The unfertil- 

 ized egg can in most cases not grow even 

 under the most favorable conditions and is 

 doomed to die in spite of its potential im- 

 mortality, unless it is fertilized or treated 

 with the methods of artificical partheno- 

 genesis. The condition of rest or growth 

 depends in this case apparently upon the 

 condition of the cortical layer of the egg 

 and the alteration in the rate of oxidations 

 connected with this condition. 



In the body, cells may be at rest or grow- 

 ing, and we do not know whether the condi- 

 tions which determine rest are identical with 



foreign cells in a body, to whieh reference was 

 made in an earlier part of this paper. 



those determining rest in the egg. "We 

 know, however, that specific substances cir- 

 culating in the blood can induce certain 

 resting cells in the body to grow and that 

 these substances differ apparently for dif- 

 ferent types of cells. It may be that in the 

 body substances antagonistic to these may 

 enforce the inactivity of the cells. 



And finally we come to the conclusion 

 that the circulation in animals or the flow 

 of substances in plants is an important 

 factor in the phenomena of cell rest and cell 

 growth, inasmuch as circulation or flow 

 determine or influence the distribution of 

 formed cells or non-formed elements which 

 induce or influence growth. The phenom- 

 ena of regeneration seem to find to a large 

 extent their explanation in the fact that a 

 wound or mutilation leads to a gathering of 

 formed or non-formed elements in spots 

 where without the mutilation they would 

 or could not have collected. 



Jacqxies Loeb 



The Kockefeller Institute foe 

 Medical Eeseaech, 

 New York 



ALASKA 8VEVEYS AND INVESTIGATIONS 

 The United States Geological Survey is 

 dispatching 12 parties to Alaska to continue 

 the systematic surveys and investigations that 

 have been in progress for the last eighteen 

 years. Of these parties three will be sent to 

 southeastern Alaska, one into upper Chitina 

 region, one to Port Valdez; two will work in 

 the Tumagain Arm-Knik region; one will 

 make investigations in the Tukon-Tanana re- 

 gion, and two in the Ruby-Kuskokwim region, 

 and another will traverse the little-known area 

 lying between the Ruby district and the Tan- 

 ana River. One party will be engaged in gen- 

 eral investigations in different parts of the 

 Territory. These parties will sail from 

 Seattle during May, so as to take full advan- 

 tage of the field season. All the men needed 

 for the work have been engaged, and the pur- 



