426 Dr. A. Krolin on the Development of the Cirripedia. 



lopment during ray residence in Madeira. It is probably the 

 young of a Balanide. 



In the older larvae of this kind (fig. 1) the anterior body is o: 

 considerable size, and the carapace is furnished at the anterior 

 margin with two moderately long horns, and at the posterior 

 margin with two spines directed obliquely upwards, which are 

 wanting in younger larvae.. The caudiform appendage is armed, 

 about halfway to its apex, with four lateral spines of consider- 

 able size arranged in two pairs, and is a good deal thicker than 

 the spinous process, especially in its anterior incrassated half. 

 In still further advanced larvae the carapace appears enlarged 

 and much arched. 



One day a larger and still further developed larva of the same 

 kind was captured; its close examination gave the following 

 results : — The carapace was now so far changed from its former 

 state, that it extended further down, and thus enclosed the body 

 on both sides. The caudiform appendage appeared strongly 

 inflated in its anterior longer portion, reaching somewhat beyond 

 the above-mentioned pairs of spines. On the lower surface of 

 this portion six pairs of processes, arranged close together in a 

 row, could be distinguished through the skin ; each of these con- 

 sisted of a comparatively long peduncle and of two short branches 

 terminating in rounded ends, issuing from it. Close behind 

 the last pair, another much shorter process, with two projections 

 similar to the branches of the longer processes, shone through 

 the skin. Both the projections, as well as the above-mentioned 

 branches, appeared to be set with thin offshoots or filaments, 

 which were recognized as the rudiments of so many setae. 

 With regard to the signification of these processes I could not 

 long remain in doubt ; they were evidently the swimming feet 

 in course of development, and the base of the caudal process the 

 subsequent Cypris-\ike form. It followed, therefore, that the 

 whole inflated part of the caudiform appendage was to be re- 

 garded as the rudiment of the future thorax. On each side, in 

 the same line with the original simple eye, now become larger 

 and enveloped by a very dark pigment, a roundish organ was 

 distinguished, containing several scattered deposits of reddish- 

 yellow pigment. The opinion forced itself upon me at once that 

 these two structures could only be the rudiments of the compound 

 eyes, which indeed was soon confirmed, as I succeeded in ob- 

 serving the gradual conversion into the Cypris-iovm in the same 

 larva. 



On the third day after the capture of the larva, I saw the 

 carapace prolonged so far backwards as to form a roof over the 

 entire anterior portion of the caudiform appendage. The simple 

 eye had become still larger, whilst the pigment-deposits in the 



