94 PETER OKKELBERG 



in reactions in the protoplasm of the cells or may so change the 

 whole metabolism of the organism that the visible results might 

 be quite different. An analogy may be drawn between the phe- 

 nomena of sex and those of the red-flowered Primula which, ac- 

 cording to Klebs ('03) becomes white when grown at high tempera^- 

 tures. In this case the two color potencies are present in the 

 organism, and which one shall appear depends upon an external 

 factor, namely, temperature. Similarly, sex potencies may 

 assert themselves differently under various conditions, so that a 

 reversal may take place, or intermediates be formed, such as are 

 found in cyclostomes and amphibians, and possibly in many 

 fishes as well. 



d. Hermaphroditism and sex reversal due to external condi- 

 tions. Another interesting case showing the double sex poten- 

 tiaUty of early larvae is recorded by Baltzer ('14). He found in 

 Bonellia viridis, the males of which live parasitic upon the 

 females, that if the larvae have a chance to attach themselves 

 to a female they become males, and if they do not succeed in 

 becoming attached they form females. If they are allowed to 

 attach themselves and are later removed, they become hermaph- 

 rodites. In the attached larvae the sex determining substances 

 are undoubtedly taken up from the host, since the female-deter- 

 mining substance seems to be stronger in the free-living state. 

 Baltzer concludes that sex is partly predetermined and partly 

 epigenetic, and that both sex tendencies are inherited but in dif- 

 ferent degrees. He believes that the male tendency is stronger 

 than the female. If this be so, we have here a case of sex rever- 

 sal, providing the larva remains unattached. A case somewhat 

 similar to that of Bonellia is that of the protandric hermaphrodite 

 Crepidula plana, in which Gould ('17) finds that the develop- 

 ment of the male phase is dependent upon the presence of a 

 larger individual of the same species, but not necessarily a female. 

 In the absence of a larger individual, the larva develops into a 

 female, but the process of transformation in the female direction 

 may be halted at any time, up to the period of formation of grow- 

 ing oocytes, by bringing the animal into proximity with an older 

 individual. Gould does not offer any explanation as to the nature 



