482 Miscellaneous. 



after the fashion of those of fishes *. This is a manifest error, as 

 the eggs of Palmgenia virgo, collected by us immediately after their 

 deposition on the piles of the quays of the Garonne, underwent 

 development in little artificial lakes. 



Reaumur asserts that he was several times witness to the copula- 

 tion of Palivgenia virgo ; but the few words he says about it prove 

 that he did not sufficiently observe it. De Geer is more explicit ; 

 but his description is so vague as to leave doubts in the reader's 

 mind. Lastly, M. Pictet, the author of a splendid monograph of 

 the Ephemeridte, is completely silent with regard to the important 

 act in question, probably because he never witnessed it. We have 

 been no more fortunate than the learned Genevese Professor ; and 

 Calori was not more successful. 



More favoured than his predecessors, Eaton has described, as an 

 eye-witness, the aerial amours of the insects under consideration. 

 According to him the male seizes the female with his abdominal 

 forceps, compels her to yield to his desires, and fecundates the ova 

 in the ordinary manner. 



When examined separately, the eggs resemble small semitrans- 

 parent grains of sand of a yellowish white colour and of an ovoid 

 form, with the smaller extremity surmounted by a sort of hood, of 

 a brown colour and spongy consistence, formed of tubes or cells 

 arranged concentrically, in the midst of which we have thought we 

 could perceive the micropyle. The diameter of the ogg is scarcely 

 ^ millim, The shell is rather hard, and resists the decomposing action 

 of the water for a long time, even after hatching. The vitellus 

 consists, as usual, of a multitude of granules and oilj' drops, destined 

 partly for the formation of the organs, and partly for the nutrition 

 of the young individual. 



It is always towards the large end of the egg that its development 

 commences ; it is there that the vitelline globules become converted 

 at first into a finely granular blastoderm. In this region the egg 

 becomes more transparent ; and from the fifth to the sixth day of 

 incubation we vaguely discern the part that will become the head. 

 This detaches itself in the form of a crescent upon the dark ground 

 of the vitellus ; then a few days afterwards the abdomen appears 

 at the opposite pole of the egg, its segmentation always much pre- 

 ceding that of the thorax, and always commencing at its setigcrous 

 extremity. The caudal setae themselves appear early. 



At first we see neither eyes, mouth, nor antennae in the blasto- 

 dermic mass which represents the head ; but as soon as the eyes 

 have appeared in the form of black spots composed of fine granules 

 of that colour, or even a little earlier, we see rising from the lateral 

 parts of the head tubercles or appendages representing the mandi- 

 bles and the maxillae. The labrum and labium appear much later. 



The antennae at first resemble thick conical rods, obscurely three- 



* Swammerdam expresses himself as follows on this point : — " Tum 

 ii''itur Faniella, more piscium, sua excutit ovula, qt(ce deinde a mascida, 

 qui itideni prius ex aquis evolat, et postmodum teneram adlnic pelliculaui 

 in terra exult, spermatc vd lactihus eff'm^is fecund ahitur " (Biblia Naturte, 

 tome i. p. '2.JO : Leydeu, 1737). 



