January 28, 1916] 



SCIENCE 



145 



over entire surface, being in the male dark brown 

 with large lateral spot (vitta) of bright yellow 

 on each side, and in the female gray with only 

 faint indication of vitta. 



In parasitized males, color of pronotum corre- 

 sponds to that of normal female. Not only is yel- 

 low lost from vitta, but characteristic pigment of 

 female develops. Vitta of normal male is yellow 

 because chitin is transparent (shows no melanin 

 even in punctures), allowing a yellow hypodermal 

 pigment (non-melanic and easily destroyed by 

 acids and other organic solvents) to shine through. 

 Punctures have no yellow pigment below them. 

 In female vitta is gray because punctures are 

 brown (due to melanin in superficial layers of 

 chitin), and hypodermal areas are partially filled 

 with grayish residue in cells and greenish pigment 

 unevenly scattered. These female characters are 

 assumed by fully parasitized males and the degree 

 of change depends upon how long before its final 

 moult the nymph was parasitized. Thus all inter- 

 mediate stages of disappearance of yellow pig- 

 ment and assumption of melanin have been foimd. 



Normal female of thelia is larger than normal 

 male; and abdomen and wings, less melanic. 

 Measurements of pronota, wings and abdomens, 

 show that parasitized males are larger than nor- 

 mal males, but not as large as normal females. 

 There is also a reduction of melanin in abdomen 

 and wings of parasitized males. Abdomen as- 

 sumes pointed form of female, and posterior chi- 

 tinous rings increase in length. 



Internally, testes undergo fatty degeneration, 

 and are finally entirely lost (either before or after 

 final moult), although cell divisions (often abnor- 

 mal) continue up to last vestige. Entire abdomen 

 of male becomes crowded with fat, in which para- 

 sites are imbedded. Normally only female ab- 

 domen contains much fat, while that of male is 

 almost entirely filled with testes, vas deferens and 

 seminal vesicles. Assumption of female secondary 

 characteristics by male must be due not only to 

 loss of primary sexual organs, but also to changed 

 metabolism (laying on of fat) caused by action of 

 parasites themselves. 



Differentiation and Dedifferentiation in Bursaria 

 and its Significance: E. J. Lund, University of 

 Minnesota. 



During the process of regeneration of pieces of 

 Bursaria a simplification of structure of the cut 

 piece always takes place previous to differentia- 

 tion. A similar process is evident during encyst- 

 ment and excystment, during normal division and 



sometimes periodically during the life of a normal 

 individual. 



The only conceivable ways, looked at from the 

 standpoint of physical science, that "regulation," 

 "regeneration," "making over," etc., of a com- 

 plex structure can take place is: (1) (a) that it 

 is first simplified physico-ehemieally to a greater or 

 less extent; (6) that the products resulting from 

 simplification are necessary and sufficient for the 

 production of a different structure; (c) that these 

 parts (resultant products, perhaps amino acids or 

 simpler proteins, etc.) be capable of recombination 

 in a different way, or (2) that a stereoisomeric 

 change takes place in the system. But the lattsr 

 is obviously insufficient to account for the changes 

 actually taking place in regulating structures, and 

 is not what would be expected from a knowledge 

 of many chemical facts of metabolism. This state- 

 ment of regeneration processes does not imply that 

 antecedent properties which determine the specific 

 path of differentiation (determiners of heredity) 

 of the morphologically non-differentiated cell do 

 not exist, nor that they are variable or invariable 

 if they do exist. 



Light Reactions of Diemyctylus : A. M. Eeese, 

 West Virginia University. 



Diemyctylus is negatively phototropie to a 

 marked degree at ordinary temperatures. At a 

 temperature near 0° C. and at a temperature of 

 about 36° C, it is more or less indifferent to 

 light. The response is the same when the light 

 comes from below. 



It is positively phototactic to lights of all in- 

 tensities, though this seems to vary with the dif- 

 ferent seasons. Experiments are now under way 

 to determine this. At low temperatures the photo- 

 taxis may be inhibited or reversed. 



It responds to red, green and blue lights as to 

 white light, the response being less marked to 

 green than to red, and still less to the blue. 



Diemyctylus responds promptly to a spot of sun- 

 light thrown upon various parts of the body by a 

 small mirror, as has been noted by the author for 

 Necturus and Cryptobranchus. 

 On Loss of Cell Pigment as an Index of Permea- 

 bility Changes: W. J. Crozier, Bermuda Bio- 

 logical Station. 



Experiments with tissues of the nudibranch 

 Chromodoris zebra give evidence showing that, at 

 least in this case, which has the advantage of be- 

 ing uncomplicated by strong muscular contraction, 

 the outward diffusion of cell pigment can not be 

 used to estimate permeability increase quantita- 

 tively. The speed with which the pigment appears 



