i>4 NOTES OX LACHNOSTERNA. 



(1) Larger, natural groups, show a typical form of penis, but not always. 



(•<J) The naturalness of certain genera can often be demonstrated by the peculiar 

 format ion of t he pi /"■>, where i here is ;i luck of ol her striking ch iracters; it is a sup- 

 plementary character of greal value. 



(:i) Most species, and often verj similar ones,show great, often remarkable, differ- 

 ences in th<' structure of the pi ni«. 



To these conclusions my studies induce me to give full consent, save 

 that the first may in' subject to some farther modifications or limita- 

 tions. This paper by Kraatz gives a very fair and well- written review 

 of the literature of the study of the genitalia, and is well deserving of 

 careful reading by all interested iu the study of these structures. I 

 would emphasize in addition to the conclusions above cited that the 

 characters are invariable within specific limits, and that while identity 

 of genital structure is not always indicative of specific identity, differ- 

 ence of this structure is always indicative of specific difference. 



Lacordaire is said to hive called these structures the " key to species,'' 

 and, while hardly willing to accept that dictum to its full extent, it cer- 

 tainly has proved so in Lachnostema. 



The rather remarkable result reached in the study of these organs in 

 the tonus allied to fusca, and confounded under the same name, may 

 seem indicative of a tendency to a too minute subdivision of forms upon 

 internal structures ; but here I only emphasize by them the external 

 characters which otherwise would warrant only Dr. Horn's conclusions 

 that they are individual, evanescent, and scarcely varietal. The fact 

 that in same localities two or more of the forms occur together will 

 make it necessary to collect more carefully and in larger series, and also 

 to devote more study to the separation of the species. 



The correlation of the 9 parts to the S structures will make it neces- 

 sary to devote more attention to this sex in the future, aud there is no 

 reason why, with a fresh specimen, determination from that sex should 

 not be as absolute or as easy as that of the $ . 



A difficulty in description arises from the want of a nomenclature of 

 the parts. Descriptive terms are lacking for the peculiar forms assumed 

 by the clasper of the $ , while for the 2 I have been unable to find any 

 nomenclature whatever. 



For the males, J. S. Baly has proposed a nomenclature, in Trans. 

 Hut. Soc. Loud., 1S70, p. 173, but this is not entirely applicable to the 

 present genus, and is, in my opinion, far from the best that can be pro- 

 posed. He calls the entire male organ the "telum." I propose to use 

 this term for the corneous tube inclosing the true membranous penis 

 and the other soft parts. It differs in structure in Lachnostema in that 

 it varies from a complete tube to a half cylinder, closed or open at the 

 top. I have made no use of the variations of this part, and doubt its 

 ever furnishing available characters. Surmounting this are the clasp- 

 eis. or, as Baly says, the "apex." These are the organs whose varia- 

 tions furnish the specific characters, and I believe the term clasper. ex- 

 pressive of its use, is better than the term apex, expressive merely of 

 position. What Baly calls the " valve " I have been unable to fix satis 





