66 External sexual Diferences in Ct/2)hophfhalnii 



duct, just indicated, the liquid secretion must flow out slowly and be able to spread over 

 the under surface of the flat distal part of the eminence. Although we have not had 

 any living specimen before us, we feel no doubt as to the use of the secretion of this 

 gland, which is found only in the one sex ; it must serve to render the other sex, 

 in this case the female, cognisant of the presence of the former in the neighbourhood, 

 which implies that the secretion must be, or contain, an getheric oil, which, contrary to 

 the secretion of the odoriferous glands, is probably of a not disagreeable odour'. This 

 interpretation is corroborated by the fact that, to judge from the shape of the joint, the 

 gland must be less developed in Stylocellus, that is to say in those Cyphophthalmi which 

 can see, and thus have one more means of finding the other sex. At the same time the 

 fact that this gland is found also in those species which are endowed with eyes is a 

 further proof of Cyphophthalmi being a type of essentially blind animals. 



The other set of external characters to which we alluded as being available for distinguishing 

 the sexes in all the representatives of Cyphophthalmi with which we are acquainted, is taken 

 from the genital orifice, its shape and particularly the distance of its anterior margin from 

 the third pair of coxse. In treating of the dermoskeleton we have already pointed out, as 

 one of the characters of the sub-order Cyphophthalmi, that the genital orifice is an open 

 hole, which is not covered by a niovable operculum genitale, as is the case in the other 

 sub-orders. The genital orifice offers specific characters, and we have therefore represented 

 it on figures of all the species ; from these figures it will be gathered that although an 

 operculum genitale may be said to exist in Cyphophthalmi in a morphological sense, yet 

 functionally there is none. The anterior border of the true second abdominal sternite is 

 prolonged so as to cover more or less the hindmost portion of the genital orifice, and some- 

 times this prolongation is separated from the rest of the second sternite by a groove or 

 a suture, but, as we have .said, it is never movable. In all Cyphophthalmi, hitherto known, 

 the genital orifice is longer in proportion to its width in the female than in the male. 

 But a far more trenchant character is found in the following fact. Arculi genitales are much 

 shorter in front of the genital orifice in the female than in the male, from which it follows 

 that the distance from the anterior margin of the genital orifice to the third pair of coxis 

 is in the female always many times shorter than the genital orifice itself; whilst in the male 

 this distance is at the least nearly equal to the length of the genital orifice, viz. in Stylocellus ; 

 generally it is longer than, and in Purcellia it is even twice as long as, the orifice. The sexes 

 also differ to some extent as to the size of the opening, but this character is less valuable ; 

 in Stylocellas the area of the genital orifice is not considerably smaller in the male than in 

 the female, but in Purcellia, Siro and Parusiro it is much smaller. 



Besides these characters which may be described as not only clearly distinctive in them- 

 selves, but applicable to all Cyphophthalmi, there are some others of less general occurrence. 

 In all the genera known to us, excepting Parasiro, the following further difference between 

 the sexes in the shape of the genital orifice may be noticed ; in the male the ridges on 

 arculi genitales are continued so far forward that they almost reach the anterior border of 

 the genital orifice, or even, as in Pettalus and Purcellia, a considerable distance beyond it ; 



1 To prevent a possible misinterpretation, we observe that which the gland is the largest; in several species, moreover, 



there is no possibility of this emiuentia with its gland being the distal part is bent downwards against the dorsal surface 



a kind of weapon. The distal portion of the eminence is too of the joint in a manner which renders the use of the end as 



weak to serve such a purpose, particularly in those species in a weapon impossible. 



