318 History of British Entomostraca. 



Avards bear, (Fig. 12.) At each moulting the number of segments into 

 which the body and tail are divided increase in number ; the num- 

 ber of articulations and the length of antennae increase, &c, but it 

 is not till after the third moulting that the insect is perfect and ca- 

 pable of producing its species.* 



A question has been started whether the Cyclops should be con- 

 sidered oviparous or viviparous insects ; and it appears to be one 

 of some difficulty, as they would seem from what I have stated to 

 be both. Geoffroy states that all the Monoculi are oviparous.t De 

 Geer also says they are oviparous. " However," he immediately 

 adds, " as the Monoculi never quit their eggs before the young ones 

 are hatched, we may perhaps regard them as viviparous."^: Jurine 

 says it is difficult to decide. Viviparous young, he says, increase in 

 size every day, and have constant need of a mother's care — if she 

 die, all die. As, however, the young of the Cyclops do not increase 

 in size after passing from the internal ovary, and as, from numerous 

 experiments which he details, they were found, after having passed 

 into the external ovary, to be independent of the life of the mother, 

 even if she were killed by spirits of wine — they must, he concludes, 

 be considered oviparous. § 



The process of moulting, under which the little creature frequent- 

 ly succumbs, is both interesting and curious. The new shell or 



* The recent alleged discoveries of Mr Thompson, of the metamorphoses which 

 the young of several genera of the Cirrhipedes and Crustacea undergo, have ex- 

 cited a good deal of attention of late to this very interesting subject. Accord- 

 ing tp Mr Thompson, the genus Zoea of Bosc, which figures away in many of 

 our arrangements, as one of our Entomostraca, is nothing more nor less than the 

 larva of the common crab, in its first state. ( Vide Zoological Researches, No. 

 I. and succeeding.) M. Burmeister has verified Mr Thompson's discoveries with 

 regard to the metamorphoses which the Cirrhipedes undergo ; but many doubts 

 still continue to be thrown upon his observations with regard to the genera of 

 Crustacea. One or two genera of each of the great groups of the Malacostraca 

 have been apparently satisfactorily ascertained to undergo no metamorphosis — and 

 the labours of M. Rathke, with the observations of other writers, and especially of 

 Mr Westwood, in a paper published in the Philosophical Transactions for 1835, 

 leave the matter still in doubt, and show the necessity of Mr Thompson's obser- 

 vations being confirmed before this interesting question can be settled. The 

 insects of the genus Cyclops approach so near to some of the Malacostraca, 

 however, that were we to reason from analogy alone, we might easily conceive 

 Mr Thompson's discoveries to be partly confirmed — as the changes which they 

 undergo are almost equally wonderful with any of the genera which he has made 

 the subject of his observations. 



f Histoire abregee des Insectes, p. 654. 



i Mem. pour servir a l'hist. des Insectes, Vol. vii. p. 435. 



§ Hist, des Monoc. p. 17. 



