152 BALAMIUS. 



ceans. Should these intervening forms ever be discovered, 

 I imagine they would prove to be Crustaceans, of not very 

 low rank, with their oviducts opening at or near their second 

 pair of antennas, and that their ova escaped, at a period of 

 exuviation, invested with an adhesive substance or tissue, 

 which served to cement them, together, probably, with the 

 exuviae of the parent, to a supporting surface. In Cirripedes, 

 we may suppose the cementing apparatus to have been 

 retained; the parent herself, instead of the exuviae, being 

 cemented down, whereas the ova have come to escape by a 

 new and anomalous course. 



Affinities, Value of Characters, Variatioji. 



Under the Order it has been stated that the Balanidae, 

 are, on the cirripedial type, the highest in the class ; that is, 

 they are the most complicated, but not (to use Professor 

 Owen's term) by mere vegetative repetition. Amongst 

 the Balanidae, the first section of the genus Balanus may be 

 taken as typical ; here we have the structure of the shell 

 extremely complicated, yet beautifully adapted for strength, 

 and for the protection of the included body. The cementing 

 apparatus is here, also, most complicated. I have divided 

 the Balanidae into two natural sub-families, the Balaninae 

 and Chthamalinae, in accordance with certain differences in 

 the structure of the shell and of the animal's body: 

 that this division is natural, might almost be inferred from 

 the one fact, that all the characters by which the Chthama- 

 linae differ from the Balaninae, are those by which the 

 former approaches the family of the Lepadidae j moreover, 

 certain anomalous characters in the Chthamalinae, as the 

 supplemental whorls of compartments in Catophragmus, 

 and the presence of caudal appendages in this same genus 

 and in Pachylasma, reveal this same affinity. The only 

 objection which I can see to the separation of the sixteen 

 genera into the above two sub-families, may be drawn from 

 the degree to which they blend together; thus, as far as 

 the shell is concerned, Chelonobia, in one important in- 

 ternal point of structure, tends to assume the character of 



