414 NOTES AND MEMORANDA. 



blastoderm, and otlicrtj from the endodcrm ; this is well sliown in the 

 diagram. 



Germinal vesicle 



Germinal cells 



Outer germinal cells Inner germinal cells 



(blastoderm) (primary) 



Ectoderm I'^uJoderm (endoblast) 



Mesoderm Inner germinal cells 

 (secondary) 



The inner germinal cells, which evidently correspond to the 

 migratory cells of earlier embryologists, may not be observed till 

 a very late stage in development; similar bodies have been seen in 

 the spiders, where they appear to represent the germ of the enteric 

 gland (liver-germ), which is only distinctly differentiated after the 

 embryonic stage is passed. 



Investing Elements. — In all the insects examined by Graber, the 

 blastoderm was seen to develop an investing segment, and also to give 

 rise to a cuticle, so that at a certain stage nine layers may be made 

 out in the embryo : — 



(1) Tertiary investment of the ovum. Eemains of the epithelium of the 



ovarian follicle. 



(2) Chorion. Secondary investment. Cuticle of ovarian follicle. 



(3) Vitelline membrane. Primary investment of the ovum. Cuticle of 



the yolk. 



(4) Cuticnlar investment of the germ. Cuticle of (5) \ 



(5) External cellular germ-membraue Derivates 

 (G) Internal „ „ I ^f ^{^^ 



(7) Ectoderm f ■Rlastodprm 



(8) Mesoderm Embryo Blastoderm. 



(9) Endoderm j / 



In some insects {Butterflies, Carahis) cavities may be observed 

 between the layers numbered 3 and 4, and between the inner germ- 

 membrane and the peripheral yolk, and these are filled with a sub- 

 stance different to, but developed from, the ordinary yolk. 



Tracheal System of Glomeris.— In the first of a series of papers 

 on the morphology and anatomy of the Jidida'* Dr. Ernst Voges, of 

 Gottingen, describes the arrangement of the tracheae in the genus 

 Glomeris. 



The stigmata, which are situated, in pairs, immediately in front of 

 the attachments of the legs, have a biscuit-shaped aperture, with 

 tumid edges, produced into numerous spiniform prolongations, which 

 form a sort of grating over the aperture. 



♦ ' Zool. Anzeiger,' i. (1878) .SGI. 



