296 Miscellaneous. 



indicated a very curious case of hj-permctamoriihosis in the larva of 

 CEstrvs equi. Von Siebold and Fabre have ascertained two others 

 — one in the hirvai of the Strepsiptera, the second in the Meloidae. 

 But in the cases cited by these naturalists the h}-permetamorphosis 

 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 

 Palingcnia virrjo. In fact, at this period of its existence it is com- 

 pletely deprived of several organs which woidd seem to be essential 

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

 of which is something surprising. Thus at first it has iieither a circu- 

 latory apparatus nor special organs for respiration. Its anteima; and 

 caudal setre have neither the same number of joints nor the villosit)' 

 which they subsequently acquire ; in a word, compared ^vith what 

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

 very incomplete animal. 



In this first state Paluir/enia virr/o therefore recalls the permanent 

 state of Nemov.ra trifasciata and varieffata, being, like them, entirely 

 destitute of trachean branchia?. A Uttle later its branchioe appear 

 under the form of small tubular ca;ca placed upon the lateral parts 

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

 parency, as, indeed, is the entire body. The animal then resemblo-s 

 Nemoura cinerea, or, still more, Sialis iKfarins, 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 PaliiKjcnia vin/o acquires the form of flattened lamella?, fringed 

 at the margins after the fashion of the branchise of the Llhdlnl<p, 

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

 divided into XQxy delicate branchlets. Lastly, the branchial lamellae 

 become gradually wider and more strongly fringed : the tracheae 

 make their appearance with their spiral thi'cad ; 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 1S44 in a little freshwater shrimp * 

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

 pendently of the aquatic mode of life of the Pal! ngotia;, 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 Geoffroy, who met with it in the 

 neighbourhood of Paris, and Latrcille, who never saw it, erroneously 

 arranged among the Crustacea, as it certainly respires by true 

 tracheae enclosed between two branchial laminivt. — Comptes Jiendus, 

 July 24, 1871, tome Ixxiii. p. 270. 



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



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

 of Toulouse (Juno 1/5, 1^70), is nothing but the oxcossively tutc "Bimtdf 

 it queue vn plumes" of CJoollVoy (Hist, des Ins. de Paris, "tome ii. pi. -*1. 

 tiiJT. ;{). thn Vrosopistojnu of Latreille (Nouv. Ann. du Mus. tomoii. p. 2.']). 



