296 Miscellaneous. 



indicated a very curious case of hypermetamorpliosis in tlie larva of 

 (Estrus equi. Von Siebold and Fabre have ascertained two others 

 — one in the larvae of the Strepsiptera, the second in the Meloidse. 

 But in the cases cited by these naturalists the hypermetamorphosis 

 was limited to some modification of the external form, the internal 

 organization remaining invariably the same up to the moment of 

 nymphosis. This is not the case in the recently hatched larva of 

 Palingenia virgo. In fact, at this period of its existence it is com- 

 pletely deprived of several organs which would seem to be essential 

 and even indispensable to the life of an insect, and the late appearance 

 of which is something surprising. Thus at first it has neither a circu- 

 latory apparatus nor special organs for respiration. Its anteunse and 

 caudal setae have neither the same number of joints nor the villosity 

 which they subsequently acquire ; in a word, compared with what 

 it will be a little while before nymphosis, it may be said to be a 

 very incomplete animal. 



In this first state Palingenia virgo therefore recalls the permanent 

 state of Nemoura trifasciata and variegata, being, like them, entirely 

 destitute of traehean branchiae. A little later its branchia? appear 

 under the form of smaU tubular caeca placed upon the lateral parts 

 of the first six segments of the abdomen, and of a crystalline trans- 

 parency, as, indeed, is the entire body. The animal then resembles 

 Nemoura cinerea, or, still more, Sialis lutarius, being furnished, like 

 the latter, with branchial caeca suspended from the first six segments 

 of the abdomen. 



Then, becoming still more complicated, the branchial apparatus 

 of Palingenia virgo acquires the form of flattened lamellae, fringed 

 at the margins after the fashion of the branchiae of the Libellulce, 

 and traversed, as in the latter, by a principal tracheary trunk sub- 

 divided into very delicate branchlets. Lastly, the branchial lamellae 

 become gradually wider and more strongly fringed ; the tracheae 

 make their appearance with their spiral thread ; the blood-globules 

 are formed, and the circulation is set up, as described by Cams. 



Here we have, therefore, true metamorphoses perfectly analogous 

 to those which I ascertained in 1844 in a little freshwater shrimp * 

 very common in the Canal du Midi — metamorphoses which, inde- 

 pendently of the aquatic mode of life of the Palingenice, establish a 

 somewhat unexpected transition between Insects and Crustacea. 

 The passage from the one group to the other is rendered still more 

 evident by the singular insect which my son, Emile, was the first to 

 discover in the Garonne, and which Geoflfroy, who met with it in the 

 neighbourhood of Paris, and LatreiUe, who never saw it, erroneotisly 

 arranged among the Crustacea, as it certainly respires by true 

 tracheae enclosed between two branchial laminaef. — Comptes Eendus, 

 July 24, 1871, tome Ixxiii. p. 276. 



* Caridina Desmarestii. See Ann. Sci. Nat. 2^ s^r. xix. p. 34. 



t This insect, which my son described to the Natural-Historv Society 

 of Toulouse (June 16, 1870), is nothing but the excessively rare' "Binode 

 a queue en plumes " of Geoffrey (Hist, des Ins. de Paris, tome ii. pl. 21. 

 fig. 3), the Prosapistoma of Latreille (Nouv, Ann. du Mus. tome ii. p. 23). 



