ARTIFICIAL PRODUCTION OF NORMAL LARVJE 577 



several parts, which, however, were still connected." These 

 histological examinations were not thorough enough, and it 

 was my intention to have them continued. The explana- 

 tion I gave for this phenomenon was as follows: "The 

 segmentation of the protoplasm is the effect of a stimulus 

 which the nucleus applies to the protoplasm and which 

 makes the protoplasm close around the nucleus." On the 

 other hand, if we put an egg into sea-water whose concentra- 

 tion has been raised by the addition of certain salts, the 

 protoplasm loses water, and this loss of water brings about 

 a loss of irritability. There is a certain concentration at 

 which the nucleus is still able to divide, while the protoplasm 

 loses its ability to respond to the stimuli emanating from 

 the nuclei. This, it seemed to me, was what happened in 

 the more concentrated sea-water. The nucleus divided, but 

 the protoplasm had lost its irritability 011 account of the loss 

 of water. Hence there existed a segmentation of the nucleus 

 without a segmentation of the protoplasm. But as soon as 

 such an egg was put back into normal sea- water the proto- 

 plasm began to take up more water and respond to the 

 stimuli of the nucleus (these stimuli I considered to be 

 chemical). Hence the protoplasm divided at once into as 

 many cells as there were nuclei preformed. 1 



The following year Morgan stated that he had repeated 

 my experiments and confirmed them, but was unable to 

 agree with me as regards the nuclear division. 2 He found 

 only one nucleus in the egg and concluded that no segmenta- 

 tion of the nucleus occurs in the concentrated sea-water, but 

 that a rapid division of the nucleus occurs when the eggs 

 are put back into normal sea-water. As he had made only 

 four experiments in ail, I asked the late Professor Norman, 

 who worked in my laboratory, to make a larger number of 



i LOEB, Journal of Morphology, Vol. VII (1892), p. 253. 



2T. H. MORGAN, Anatomischer Anzeiger, Vol. IX (1894), p. 141. 



