496 LIFE : OUTLINES OF GENERAL BIOLOGY 



the part of the male Cervida;; they necessarily became part of the 

 inheritance of the females as well ; but they could not find expression, 

 so to speak, in the female constitution. According to Tandler, how- 

 ever, they were originally possessed by both sexes, like the horns of 

 cattle, and have in the course of time become sex-linked characters, 

 normally developed in the males only, except in the old-fashioned 

 reindeer, where they occur in both sexes. 



Kammerer comes to the same conclusion: "The sex-characters 

 simply form a particular group of species-characters: all sex- 

 characters are at the same time species-characters." At the same 

 time he refers to Mobius's thesis that there is a sort of somatic sex, 

 a sex-ditferentiation of all the organs and tissues, whether they 

 show a visible difference or not, so that one may, he says, invert the 

 previous sentence and say that all species-characters are also sex- 

 characters. But, in any case, he holds that there are certainly no 

 special sex-characters, which stand apart from other species- 

 characters, as things per se and autonomous. 



In their important work Die biologischen Grundlagen der sekun- 

 ddren Gcschlechtscharaktcrc, 1913, Tandler and Gross are very 

 emphatic in their conclusion that all sex-characters have been 

 derived from specihc characters or "systematic" characters, which 

 in the course of time have been brought (by the usual method of 

 variation and selection) into the service of reproduction. This 

 occurred at different periods, as is suggested by their different 

 degrees of variability to-day. And pari passu with their evolution 

 they have come into correlation with the gonadial glands of internal 

 secretion which supply their indispensable liberating stimuli. "The 

 secondary sex-characters are to begin with systematic characters 

 and they ultimately owe their development and dillerentiation to 

 the harmonious co-operation of the glands of internal secretion." 



But this thesis that: " All secondary sex-characters were at first 

 specific characters", appears to us to be an exaggeration of a sound 

 idea. 



There are, it seems to us, numerous peculiarities of one sex or the 

 other which cannot be readily derived from specific characters 

 supposed to be common to both .sexes. And if it be said that the 

 cases we would adduce are not fair samples of sex characters, we 

 would reply that it is very difhcult to draw a line round "secondary 

 sex-characters", separating them from other sex differences. This is 

 especially difficult among Invertebrate animals, where we have 

 almost no knowledge of glands of internal secretion connected with 

 the essential gonads, and are therefore bereft of that useful criterion 

 of a secondary sex-character which has been discovered in 

 Vertebrates. 



Let us consider, then, a few striking sex differences in the light 

 of Tandler's theory. The female PajKM-nautilus (Argonauta) is very 



