July 19, 1007] 



SCIENCE 



87 



invariably amputated. The limb on the op- 

 posite side of the body was thus given every 

 possible advantage with regard to growth, in 

 order to see whether this chela could be made 

 to differentiate into a crusher. The data so 

 far obtained for these specimens is in the 

 table given above. 



From this table it will be observed that in 

 over 90 per cent, of the specimens the chelae 

 have already differentiated asymmetrically, 

 but in no case for group A did a crusher 

 develop on the right side, or in group B, a 

 crusher on the left side. The evidence for 

 specimens Nos. 3 and 9 is at present neutral, 

 for they still appear to retain their embryonic 

 symmetry, and it remains to be seen at the 

 next moult, which will occur during the 

 spring, whether they too will finally develop 

 a crusher on the right side or not. At any 

 rate, this experiment clearly shows that in all 

 cases where the chelae have differentiated far 

 enough to display asymmetrical characters, the 

 crusher has developed on the chela which was 

 given the greater opportunity for growth; i. e., 

 on the side which was not mutilated. 



The results so far attained, therefore, estab- 

 lish a strong presumption that the " right- or 

 left-handedness " of the lobster may not be 

 entirely predetermined in the egg. If these 

 results are confirmed by further experiments, 

 it ought to furnish convincing proof that 

 the asymmetrical relation of chelae in the 

 lobster may under certain conditions, at least, 

 be determined by other than hereditary 

 factors. 



This result is especially interesting in view 

 of the fact that in the adult lobster we do 

 not seem to meet with the phenomenon of 

 reversal or compensatory regulation which 

 Zeleny" and Przibram™ have found in other 

 Crustacea. In the course of my experiments 

 I have mutilated over 200 adult lobsters in 

 which the normal asymmetrical limbs were 

 autotomously removed and presei-ved for each 

 specimen, but in no case did a crusher ever 

 regenerate on the side which had originally 

 carried a nipper and at the same time vice 



^^Loc. cit. (17). 

 "■'Loc. cit. (7). 



versa for the nipper. It has been suggested 

 that possibly one reason why we do not get a 

 typical reversal in the lobster is because the 

 asymmetry of chelfe consists in a greater 

 qualitative differentiation than in the case of 

 the crabs and some other decapod Crustacea, 

 consequently, a true reversal in the lobster 

 would involve more fundamental morpho- 

 logical transformations than in the case of 

 these other forms. On the other hand, in the 

 larval lobster the chelfe are very similar both 

 qualitatively and quantitatively, and the re- 

 sults of our experiments seem to indicate that 

 the symmetrical relations of the organisms 

 are at this stage in a much more plastic 

 condition. 



We may summarize, then, this discussion of 

 regeneration and the origin of symmetry as 

 follows : First, positive evidence has been ad- 

 vanced that the process of regeneration is an 

 important factor in the origin of symmetrical 

 chelse. Second, the results of the foregoing 

 experiments on the larval stages establish 

 a strong presumption that the right- or left- 

 handed asymmetry of the lobster, instead of 

 being entirely hereditary, may be influenced 

 during ontogenetic development by external 

 factors. V. E. Emjiel 



Anatomical Laboratory, 

 Brown" Uni\'ersity, 

 Provirexce, R. I., 

 March 6, 1007 



DIE BACK OF THE PEACH TREES 



(Valsa leucostoma Pers.) ' ■ 

 Die back is a serious enemy of the cherry 

 orchards of Germany. Ij is especially de- 

 structive in the districts along the Rhine. It 

 is also reported as being parasitic on the stone 

 fruits of Australia. Professor F. C. Stewart, 

 of the New York Agricultural Experiment 

 Station, was the first American to call atten- 

 tion to the parasitic nature of this fungus. 

 Ellis and Everhart in their ' North American 

 Pyrenomycetes ' state that this organism is 

 found on peach, plum and almond trees in 

 Carolina, Pennsylvania, New Jersey and prob- 

 ably throughout the country where the trees 

 are fotmd. 



Experiments at this station show that it 



