202 CARNEGIE INSTITUTION OF WASHINGTON, 



individuals of other species are found in cultures at the time of their maximum 

 concentration. 



The method of treating amoebas with varying dilutions and concentrations 

 of sea-water for the purpose of detecting specific differences, which was dis- 

 covered in 1919, has been applied to all the new species discovered this season, 

 with even better results than had been hoped for. Some species very similar 

 in general appearance are found to react in a strikingly different manner to 

 diluted sea-water. Tliis test has proved to be one of the most important for 

 the quick and accurate determination of species. 



After the season at the Tortugas Laboratoiy was over, a few weeks were 

 devoted to examining amoebas found at Cold Spring Harbor, New York, to 

 obtain evidence on geographical distribution. Of the 20 species reported 

 from Tortugas, 5 were found at Cold Spring Harbor; 5 new amcebas were 

 also found, 2 of them being very common, while the other 3 were relatively 

 rare. Several other new species were observed, but they could not be de- 

 scribed adequately for want of time. The indications are, therefore, that 

 amcebas are subject in their geographical distribution to general principles, 

 similar to those that govern the distribution of many other groups of animals. 



Studies on the Pieridce, New Mutations in Colias philodice, by John H. 



Gerould. 



In August 1920 about 45 conspicuous blue-green caterpillars developed in 

 three cultures of the common sulphur butterfly, Colias philodice, that had 

 been inbred for two generations in the study of the inheritance dimorphism 

 (white wing-color) in the female. 



The normal grass-green color of the caterpillars of this species is due to the 

 pigments in the hemolymph derived directly from chlorophyl of the food- 

 plant (clover). The hemolymph of the mutant caterpillars, however, as 

 well as the hypodermis, is blue-green. The pupa is Hkewise bluish, instead of 

 yellowish grass-green. The eye-color of the adult also is bluish green, not 

 yellow-green; the hemolymph color of the butterfly is identical with that of 

 the mutant caterpillar, blue-green. The pigments of the hemolymph cor- 

 respond in both the mutant and normal butterfly to the (hypodermal) color 

 of the compound eye. 



The egg laid by a female with blue-green hemolymph is of a brilliant pure 

 white, not the normal cream-white. The cocoon color of braconid larvae that 

 have parasitized the blue-green caterpillar, fed upon the blue-green blood, 

 and emerged to spin upon the surface of the dying caterpillar, is pure white, 

 lacking the bright yellow color of the normal cocoon. 



Blue-green hemolymph thus lacks a yellow pigment, probably derived nor- 

 mally from xanthophyl. This is not the yellow pigment of the wing-color, 

 which is known to be a derivative of uric acid deposited in the scales upon the 

 wing, for the wing-color of butterflies having the blue-green hemolymph is 

 of the normal yellow color, unaffected by this mutation. 



Blue-green hemolymph is a simple non-sex-hnked Mendelian recessive. 

 Originally produced by two generations of inbreeding from a female presum- 

 ably heterozygous for it, blue-green individuals thus far have proved nearly 

 sterile. When fertile, they breed true. They are vigorous as caterpillars 

 and adults, but they lack almost completely the instinct for mating. 



The blue-green caterpillars that hibernated in 1920-21 produced butter- 

 flies that failed to mate, but fortunately several females of the same stock 

 survived from a pair of grass-green parents of which the male was known to 

 be heterozygous for blue-green. To save the race, these surviving females, of 

 which presumably one-half were heterozygous for the blue-green, were mated 



