REPORT ON ZOOLOGY. 225 



out several remarks respecting the arrangement and affinities of 

 these animals in general. Quoy and Gaimard have communi- 

 cated some new observations relating to the habits and anatomy of 

 the Salpee which they made during their voyage withFreycinet*. 

 Audouin and Edwards, who paid great attention to the Compound 

 Jiscidice during their residence on the Chausey Islands, have 

 made some interesting discoveries respecting the mode of de- 

 velopment of these animals f . They have ascertained that, al- 

 though in their adult state they are united to form one common 

 mass, and are immoveably fixed to some rock or other marine 

 substance, they enjoy at birth a separate individuality, and are, 

 moreover, endued with the power of swimming freely in the 

 water from place to place. It is not till after two days that this 

 locomotion ceases. They then seek a place favourable to their 

 further development ; and while some return to the parent mass 

 from which they first emanated, others attach themselves afar 

 off and found new colonies. These observations are of great 

 value. They not only throw light upon the history of these ani- 

 mals, but serve to establish very important relations between 

 them and other groups in which similar facts have been noticed, 

 connected with the early development of the young. Dr. Meyen's 

 researches are confined to the genus Salpa, which forms the sub- 

 ject of a memoir by him in the Nov. Act. &fc. Nat. Cur. for 

 1832 X- He has revised the characters of more than thirty 

 species. 



6. Cirripeda. — ^The doubtful situation of this class has been 

 already alluded to. Indeed there are few groups whose true 

 affinities have been involved in so much uncertainty. The most 

 recent observations, however, seem decidedly in favour of the 

 opinion of those naturalists who regard it as partaking more of 

 the Annulose than the Molluscous structure, and approaching, 

 on the whole, nearest to the Branchiopod Crustacea. Straus 

 was the first to announce this affinity in his memoir on the genus 

 Daphnia, published in 1819. He was led to observe it from a 

 comparison of the relative structures of the genera Pentelasmis 

 (Leach) and Limnadia (Brong.). Two years afterwards, Mr. 

 MacLeay, apparently without knowledge of Straus's memoir, 

 pointed out the same relationship §, dwelling, however, more 



articularly on the affinity between Pentelasmis and Daphnia. 



am not avvare that anything further was written on this sub- 

 ject till 1830, in which year Mr. Thompson published the third 



• Ann. des Sci. Nat. (1825), torn. vi. p. 28. ; and Bull, de la Soc.Philom. 

 (1826), p. 123. 



t See Ann. des Sci. Nat., torn. xv. p. 6. 



J torn. xvi. p. 363. § Hor. Ent., p. 308. 



1834. (i 



r 



