396 William Morton Wheeler 



Owing to the limits of this paper and to the fact that the depend- 

 ence of the secondary on the primary sexual characters in verte- 

 brates has been recently analyzed by several authors, notably^ by 

 Herbst ('01) and Cunningham ('08), I shall confine my remarks 

 very largely to the arthropods. Taking the word "castration" 

 in the broad sense suggested above, we may distinguish: 



1. Surgical, or true castration, i. e., the sudden and complete 

 ablation of the male or female gonads, so that the organism is 

 deprived of its primary sexual characters, if we do not include 

 in this term also the gonad-ducts and copulatory organs. This 

 operation is of the greatest experimental significance, since, when 

 performed at the proper ontogenetic stage, it has been shown to 

 lead in many animals to interesting modifications ot the secondary- 

 characters of each sex. 



2. Physiological castration. Under this head may be included 

 at least three diflFerent forms of inhibition in the development of 

 the gonads, leading to a failure of the individual to develop its 

 primary sexual characters, or, in other words, to an inability to 

 function as a male or a female. This inhibition is brought about 

 by an insufficient supply of nutriment and appears as the result 

 of a well-known law, according to which the organism provides 

 in the first instance for the growth and difi^erentiation of its soma 

 and develops its gonads on the nourishment in excess of that 

 required for normal growth in stature and the complete differ- 

 entiation of the various tissues. The following three forms of 

 physiological castration may be distinguished: 



A. AHmentary castration. This term was originally given by 

 Emery ('96) to the suppression of gonadic development through 

 insufficient feeding of the organism during its larval life. 



B. Nutricial castration. This term was first used b)' Marchal 

 ('97) to designate the maintainance of the gonads in an undeveloped 

 condition in the adult, owing to the latter's devoting itself to 

 nursing the brood of other fertile individuals instead of itself 

 taking on the reproductive function. 



C. Phasic castration. 1 use this term, for lack of a better, to 

 include all the cases in which the gonads are inhibited in their 

 development by seasonal or ontogenetic (growth) conditions. This 



