334 PHYSIOLOGY. 



210. 



After impregnation, by means of copulation with the male, the 

 successive development of the egg germs,lying in the tubes, consecutively 

 ensues, namely, one after the other. Joh. Muller * has instituted 

 admirable observations relative to this development in Phasma gigas, 

 and of which we shall here make an abridged extract. 



If for this purpose we return back to the anatomical description of 

 the ovaries, we shall there find an already indicated connexion of the 

 egg tubes with the dorsal vessel. The mode of this connexion is thus : 

 a delicate, but, by its structure, strong filament, passes from the 

 superior extremity of each egg tube to the wall of the vessel, which is 

 a continuation of the heart, and which we have described as the aorta, 

 and it there unites itself to it. This connecting filament the discoverer 

 Joh. Muller considers as a vessel which, passing from the aorta, trans- 

 pierces the extremity of each of the egg tubes, and thence forms its 

 internal coating. He further considers that the material which deposits 

 the egg germs comes from the aorta through these connecting filaments, 

 and that this connexion is of the greatest importance to their develop- 

 ment. Howsoever apparently just these conclusions may appear, they 

 have nevertheless an hypothetical origin. Nothing further is certainly 

 evident from his representation, than that a continuation of the egg tubes 

 in many, but not in all, cases, is attached to the dorsal vessel ; but that 

 these filaments are vessels which open into the dorsal vessel is not 

 proved, for he did not see the contents of the dorsal vessel pass into 

 these connecting filaments, which, indeed, in insects preserved in spirits 

 of wine, would be very difficult to detect. To attach, therefore, less 

 importance to this, the direct transformation of a blood-vessel into an 

 egg tube, appears inadmissible, for then the egg germ must be developed 

 in the blood-vessel, which merits certainly not the least attention. 

 Indeed, the same skilful observer has regularly found in the common 

 leech (Hirudo vulgaris) the nervous cord in the cavity of a central 

 blood-vessel f ; but this certainly cannot be cited as an analogy to the 

 transformation of a blood-vessel into an egg tube, which his earlier 

 discovery endeavours to prove, and a more analogous case is much less 

 to be found. I therefore consider this supposed connexion of the two 

 organs as nothing else than a superficial attachment of the egg tube to 



* Nova Acta Phys. Med. T. xii. PI. II. page 620, &c. 



f Mecke!' s Arcliiv. fur Anat. uml Physiol. 1828. pp. 26 and 27. 



