No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 57 



and become greatly elongated, like the Xiphidiicrn ^^g, the 

 micropylar organ must come to lie on the same surface of the 

 yolk as the germ-band. 



It has been repeatedly suggested, and, I believe, on very 



good grounds, that the Podurid "micropyle" is the homologue 



^y:-.... of the crustacean "dorsal organ." In 



^ 0^ "% ^^ both groups the organ arises soon 



%..''••-■.# ,1 after the germ-band is mapped out on 



^^"■■"' the yolk, and m both groups it is a 



circular or oval thickening of the blas- 



..:•=•■■"-• • •.. toderm Ivino^ in the median dorsal line 



1^. _.. -j'y^ distinctly nearer the head than the 



•'«*iA .;L,J . fe--!*^ j^^ telson. In the Crustacea its centre 



j^.-y; •"_^'^'{)^ often shows a depression to the walls 



mx^ of which the Blastoderm-haut is 



— ^■^ attached, while standing away from 



V^. — ™..>^ ^YyQ surface of the egg at other points. 



■ »^ An exactly similar condition obtains 



'""Xri: in the Poduridae; a slight depression 



-^•u'^ <M>'' marks the centre of the organ in 



Amirida, while in AnnropJioriis (Le- 

 moine, '8?) there appears to be a deep 

 pit at the attachment of the chitinous 

 envelope. This depression is com- 

 r - '- '^^- parable to the depression seen in 



Fig". ^ in XipJiidium, where the cir- 

 FiG VI i3 -^ -t 



' . , . cular fold is encroaching on the 



Embryo of Anurtda mari- 

 tima spread out on a flat CllSK. 



surface, f/.^., " micropyle " /(^., Up to the Stage represented in 



labrum;/^/.,procephaiiclobe; ^j^^ figure just referred to, the indu- 



«^, antenna; /c. i?/., minute ap- . .,, , i 



pendage of the tritocerebral Slum Will bear close comparison 



segment; Wirt'., mandible; wx', with the crustaccau " dorsal Organ." 



;«x^ first and second maxillae; j^^ ^J^g f^j-g^ stages of its spread- 

 ■p'^-p'^, first to third thoracic . -^ 1 ui 4. t. *. 



^ "^ ' , ^ . 1 J ms: it also resembles to some extent 



appendages; a/S first abdom- » 



inal appendage (= left half of the saddle-shaped " dorsal organ" 

 collophore); fl/% second ab- Qf Ouisciis, PorcelHo, and Ligia. 



dominal appendage; ««., anus. -^^^^ beyond this point it differs 



widely from its homologues, and it is difficult to see why it 



