540 



PSYCHE. 



[October 1S93. 



Dytisciis fasciventris I find only 4 

 vessels, and this number is retained in 

 the imago. 



Melolontha vulgaris deserves spe- 

 cial mention, as it shows that the tet- 

 ranephric is a modification of the 

 hexanephric condition. Voeltzkow, 

 as I have said, found 6 Malpighian 

 vessels in the embryo of this Scarabaeid, 

 whereas writers on the adult and larva 

 describe only 4. A pair of vessels 

 must, therefore, be suppressed dur- 

 ing post-embryonic development, pre- 

 sumably in early larval life. The 

 bearing of this fact on the tetranephric 

 condition of Dytiscus is obvious ; we 

 have only to suppose that the tendency 

 to suppress a pair of vessels has been 

 carried back into early embryonic life. 



Lepidoptera. Schindler * and Chol- 

 odkowsky t have given us a consid- 

 erable body of facts on the number 

 and disposition of the Malpighian ves- 

 sels in the Lepidoptera. The em- 

 bryonic development of the tubules 

 was elucidated by HatschekJ, as long 

 ago as 1877. "Wir finden" says this 

 investigator, l 'im stadium C schon 6 

 Malpighi'sche driisen, jederseits drei, 

 die nach hinten zun'ickgebogen, rings 

 tun den hinterdarm auf dem quer- 

 schnitte sich zeigen (figs. 3 and 4, pi. 

 iii). Die drei Malpighi'schen dri'isen 

 jeder seite miinden durch ein gemein- 

 schaftliches aufangsstiick in das blinde 

 ende des hinterdarmes." Hatschek's 

 figures show the arrangement of the 



* 1. c. p, 646 et seq. 

 t 1. c. 



% Beitrage zur etitwicklungsgeschichie der Lepi- 

 dopteren. Naumburg, 1877, p. 19. 



vessels to be the same as in the larva and 

 imago. My own observations on em- 

 bryos of Platysamia cecropia confirm 

 his account. 



With the exception of a very few 

 species, to be considered presently, all 

 Lepidoptera have 6 Malpighian vessels. 

 They are not discrete diverticula of the 

 hind-gut, but on either side two of the 

 vessels are united by a common trunk 

 to the third, so that there is only one 

 opening into the rectum on either side. 

 This antler-like svstem appears to arise 

 in the following manner : a hollow bud 

 grows out from the proctodaeum and 

 bifurcates; then one of the two vessels 

 thus formed bifurcates, while the other 

 simply lengthens. Cholodkowsky calls 

 the duct leading into the rectum the 

 ''tronc basilaire," the one uniting the 

 two terminal vessels the "tronc second- 

 aire." He gives an extended account 

 of the relative variations in length of 

 the two trunks throughout the various 

 families of Lepidoptera. The varia- 

 tions are sometimes considerable, but 

 the number 6 is rigorously adhered to. 

 The only exceptions observed by 

 Cholodkowskv are the Pyralid Galleria 

 and certain Tineids. 



In G. melonella the Malpighian ves- 

 sels resemble two trees "richement et 

 irregulierement ramifies." This pecu- 

 liar form is so strikingly unique that we 

 may put it down without hesitation as 

 a secondary development. Cholod- 

 kowsky finds that the larva of Tinea 

 biselliella has the typical 6 Malpighian 

 vessels ; but these break down during 

 the pupal stage and in their stead arises 



