ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 197 



being more transparent than that of most Isopods, the hue of the blood 

 largely determines the colour of the animal. For this reason their 

 colour is not subject to reflex alteration, but remains fixed in spite of the 

 change of eye illumination. Even Isopods that possess chromatophores 

 may derive part of their colour from that of the blood. Tait finds that 

 pale specimens of Gammarus marinus are infected with what seems to 

 be a very large bacterium, which cii'culates in large numbers in the 

 blood. The infected animals become white in colour, owing to their 

 blood being deprived of pigment, and to reflection of light from the 

 bacteria. The animals were apparently healthy in spite of the over- 

 whelming infection. The length of the rice-grain-shaped organisms 

 was about equal to the diameter of a human red blood corpuscle. 

 Vejdovsky has described, in spirit specimens of Gammarus zschokkei 

 from Garschina Lake, Switzerland, the occurrence of a " gigantic " 

 nucleate micro-organism, which he has named Bacterium gammari. It 

 causes some change in metabolism, whereby already-formed blood pig- 

 ment is destroyed, or the manufacture of new pigment is inhibited. 



Sex Intergrades in Simocephalus.*— Arthur M. Banta has found 

 intermediate sex forms in the Phyllopod Simocephalus vetulus, which 

 reproduces for long periods parthenogenetically. It may be noted that 

 gynandromorphs are really sex-mosaics, inasmuch as a definite portion 

 of the body, frequently one half, possesses in toto the definite characters 

 of one sex, while the rest of the body is distinctively of the other sex. But 

 sex intergrades are intermediate not as sex-mosaics but quantitatively^ 

 and are as a whole different from either the normal male or the normal 

 female. Banta found forms of Simocephalus which were male with 

 one or more female secondary sex characters, females with one to 

 several male characters, and some hermaphrodites with various combina- 

 tions of male and female secondary sex characters. 



Eight secondary sex characters distinguish the female of Simo- 

 cephalus vetuhis from the male — larger size, position and size of the 

 eye, outline of the head, absence of the nuchal protuberance, features 

 of the first (rudimentary) antennge, outhne and armature of the lateral 

 post-abdomen margins. 



The sex intergrades are of almost all possible sorts. More than half 

 the individuals are neither whole male or wholly female, but possess 

 definite morphological sex characters of both sexes. Sex here reveals 

 itself not as a fixed and definite state but as a purely relative thing. 

 The usual sex balance is disturbed. Environmental factors probably 

 wield the determining influence. The disturbance influences not only 

 the individual, but also its germ-plasm, and the disturbed balance is 

 evident throughout succeeding generations. Noteworthy is the produc- 

 tion from sex intergrades of strains which produce only normal females, 

 and on occasion only normal males. 



Heliotropism of Barnacle Larvae. f — Jacques Loeb and John H. 

 Northop have experimented with these larvse, which move in a straight 



* Proc. Nat. Acad. Sci. U.S.A., ii. (1916) pp. 578-83. 

 t Proc. Nat. Acad. Sci., iii. (1917) pp. 539-44 (2 figs.). 



