12 C1RRIPEDIA, 



In the order Thoracica, including all common Cirripedes, 

 the cephalic and thoracic segments are as much confounded 

 together (but with coalescence and abortion of two middle 

 segments) as in most Podophthalmia ; but in the two other 

 orders, the cephalic and thoracic segments are as distinct 

 as in the Edriophthalmia. The number of the segments, 

 however, which strictly appertain to the anterior part of the 

 head and mouth, being only six, is an Entomostracan cha- 

 racter ; on the other hand, the first pair of cirri in the Tho- 

 racica, has some claim from their position, apparent functions, 

 and separation from the succeeding pairs, to be said to belong 

 to the mouth ; on which view, the first nine segments would, 

 in function, be cephalic, as in the highest Crustaceans. The 

 fewness of the segments of the abdomen, and their not 

 bearing in two of the orders appendages, is an Entomos- 

 tracan character. 



Cirripedes are permanently attached, even before their 

 final metamorphosis, by a tissue or cement, first debouching 

 through the second pair of antennas, and, subsequently, in 

 most cases, through special orifices, penetrating the anterior 

 part of the head ; this cement proceeds from glands, which 

 certainly are modified portions of the ovarian system. This 

 fact I consider of tlie highest classificatory importance, for it 

 is absolutely the one single character common to all Cirri- 

 pedes, besides such as show only that these animals belong 

 to the articulated kingdom, and are Crustaceans. No struc- 

 ture of this kind has hitherto been observed in any other 

 member of the class or kingdom. Even in the Suctorial 

 Entomostracans, which become immoveably attached to the 

 fish on which they prey, the males are free ; and the means 

 of attachment, as far as known, are quite different. 



Both the first and second pairs of attennas are absent 

 in the mature animal ; for the three terminal segments of 

 the antennas of the pupa, which may always be found ce- 

 mented under the centre of the surface of attachment, are 

 functionless, after maturity. The eyes are rudimentary, 

 and are singular from being seated far from the anterior 

 extremity of the head. In their rudimentary state, and 

 in the absence of antennas, we have characters common 

 with certain Suctorial Entomostracans ; and this similarity 



