No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 57 



and become greatly elongated, like the Xiphiditim ^gg, 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.y.;v,. of the crustacean "dorsal organ." In 



C.#%t. \ „3io both groups the organ arises soon 



'•-,:#' i' after the germ-band is mapped out on 



"'''^'^^*'' the yolk, and in both groups it is a 



circular or oval thickening of the blas- 



s-:":'"-- -.. toderm Ivino- in the median dorsal line 



1^. .•••••'"^ vvcX distinctly nearer the head than the 



''"^ ' ■ '"""^' \^^^ _ telson. In the Crustacea its centre 



'■^ 1 i fej\y.'.ri^"bL often shows a depression to the walls 



<4JI i^ YxvxJ of which the Blastoderm-haut is 



^|\Vis^ '"^ attached, while standing away from 



■"•'^ the surface of the egg at other points. 



'"^ An exactly similar condition obtams 



^ ^.'Z.....aYO: in the Poduridae; a slight depression 



-^i(^ — •<>''^'' marks the centre of the organ in 



0fh \^^ Amu'ida, while in Amiivphorns (Le- 



;■ --^^ ^J '-^ moine, '8?) there appears to be a deep 



pit at the attachment of the chitinous 



envelope. This depression is com- 



T ■ " -" ^^' parable to the depression seen in 



'■■■""' Fig. 3 in XipJiidimn, where the cir- 



cular fold is encroaching on the 



Embryo of Aniirtda mari- 

 tima spread out on a flat ulSK. 



surface, fl'.^., " micropyie " //^., Up to the Stage represented in 



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



aAantenna; /<:. a-/., minute ap- . •^■^ ^ ^ 



pendage of the tritocerebral S^^m Will bear close comparison 



segment; wfl'., mandible ;w-rS with the crustaccan " dorsal Organ." 



w.r% first and second maxillae; Jj^ ^^ f^j-St Stages of its Sprcad- 

 ■b^-t'^. first to third thoracic ... 1 1,1 4. „ <- «. 



-^ ^ ' , , ^ , , ins: it also resembles to some extent 



appendages; a/S first abdom- <=> ^^ 



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

 collophore); <7/^ second ab- gf Oniscus, PorcclHo, and Ligia. 

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



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



