328 Mr. C. Spence Bate on the Development of the Cirripedia. 



analogy it may be assumed, as most probable, that they exist in 

 a more or less rudimentary form in all. 



The natatory legs are at this period three on each side, the 

 anterior pair being single and formed of three or four articula- 

 tions, the terminating one being armed with three or four long 

 spines, one of which also is generally attached to each of the 

 two preceding joints. The two posterior pairs of legs become 

 duplicates after the basal joint, which is large, and generally armed 

 with a process covered with sharp spines pointing towards the ani- 

 mal : each of the joints of the larger division of the double ex- 

 tremities of both the posterior pairs is furnished with similar 

 spines, some of which are in different species more or less fringed 

 with fine ciliated processes. The spine upon the penultimate joint 

 of the posterior pair of legs is in Balanus perforatus, Chthamalus 

 depressus and Clitia Stromia curved inwards as well as ciliated ; 

 each of the extremities likewise is supplied with long spines 

 or hair-like processes, similar to those which exist attached to 

 the cirrhi in the adult. 



It is since these observations have been made that I have be- 

 come aware of Prof. Goodsir^s paper in the ' Edin. New Phil. 

 Journal,^ by which I perceive that his observations do not exactly 

 coincide with my own ; but I think that much of the difference 

 may depend upon the circumstance of his having viewed the 

 animal from the dorsal surface only; since, if he had seen the ani- 

 mal from beneath, he would have observed that the anterior legs 

 originate from a similar position with the rest, that is, near the 

 centre of the animal. Of the " large segment which (he says) 

 has originated at the anterior part of the body after the first 

 moult,^^ I have not been enabled to convince myself. That a 

 line across may sometimes be seen in the dead animals, t am 

 aware ; but the fact of its position being not always persistent has 

 induced me to attribute the appearance to an accidental fold in 

 the tunic of the animal, originating in the roughness of mani- 

 pulation in mounting the specimens. 



Again, in Prof. Goodsir's figure the whole extremity of the leg 

 consists of but a single articulation, whereas it has appeared to 

 ine to be, like the others, made up of several. The large basal 

 ])rocess of the second pair of legs is not given in the same figure ; 

 this, together with his not having observed the abdominal pro- 

 cess, is but the natural result of the drawing being made of the 

 dorsal surface only. 



Unfortunately, from the period of the larva having obtained 

 its second form, which, according to my own experience, takes 

 place on the second and not the eighth day, as stated by Prof. 

 Goodsir, — and this I found invariably to be the case in every spe- 

 cies which I have observed, — 1 have not been able, even with the 



