Mr. C. Spence Bate on the Development of the Cbripedia. 325 



very successful, and which has enabled me to accompany this 

 paper with sketches of the larva of five separate species : — 



1. Balanus balanoides, Linn. 



2. B. porcatus, Da Costa. B. sulcatus, Brut/. B. Scoticus, Wood, 



3. B. perforatus, Brug. B. communis, Mont, B. (var.) Cranchii, 



Leach. 



4. Chthamalus depressus (?), Poli. Balanus punctatus, Mont, 



5. Clitia Stromia, Miiller. Balanus verruca, Mont. 



Upon- placing the young as soon as hatched under the mi- 

 croscope, I was interested to find that it differed as much 

 from Mr. Thomson's figure as that given by him does from the 

 adult animal*, thus showing that the larva must pass through 

 more than one metamorphosis prior to its assuming the figure of 

 the adult. 



There is, on the first appearance of the larva of the Balani, a 

 single black spot in the eentre of what would be termed the head 

 of the animal, appearing like the eye in Cyclops, Canthocamptus, 

 &c. ; but this it cannot be, since the form is not persistent in 

 every individual evert of the same species. With what agency this 

 spot may be endowed I am not capable of stating, but it appears 

 to me to be analogous to a similar spot in the larva. of Chiro- 

 cephalus diaphanusf, and which, by development, is shown to 

 have no connection with the eyes ; so also in an older stage in 

 the larva of the Balanus, the eyes, which are absent in the young, 

 become fully developed, but are found to exist distinct from this 

 spot, which has been looked upon as an organ of vision by all pre- 

 vious observers. I think, however, that we are scarcely justified 

 in assuming every black spot in a convenient position to be an eye : 

 and in this instance, when the spot may be seen in the young of 

 the same parent to put on almost every modification of form, I can 

 scarcely bring myself to subscribe to the idea of its being an agent 

 of sight. Moreover, in the pupa state, when the eyes are large 

 and conspicuous, there may be observed a spot (PI. VIII. fig. 15, 

 16 b) upon the shell, the same which Mr. Thomson presumes to 

 be the " nucleus of the future attachment," so like to that to 

 which we allude in the larva, that I am inclined to believe 



* When this paper was first written, I was ignorant of the discoveries of 

 either Burmeister or Goodsir $ the researches of the former I have only 

 seen since this has been in type ; and to both of whom separately is due the 

 merit of the discovery of the great fact of the complex metamorphosis of 

 the Cirripedia; since Mr. J. V. Thomson, although the original discoverer 

 of both stages, did not even conjecture that there was more than a single 

 metamorphosis, although he was aware of the fact in the marine Decapoda, 

 attributing the earlier form or larva to the pedunculated division, and the 

 latter or pupa to the sessile division of the Cirripedia. 



t Vide figures by Dr. Baird in the ' Hist, of British Entomostraca.' 



