240 SCALPELLUM VULGARE, 



of this border, on the edge of the tunic of the sack, and 

 that by the action of the cement, the corium beneath 

 is killed (as I believe always is the case with other para- 

 sitic Cirripedia), whereas on both sides, the chitine con- 

 tinues to be added to, so that the male, excepting the 

 upper and always projecting portion, becomes imbedded 

 at first laterally, and ultimately all round : I have seen 

 specimens in several different stages of imbedment. 

 Hence, in old specimens, with a thick and broad chitine 

 border, it might and does come to pass that one male is 

 imbedded (the valve being laid flat) directly beneath 

 another. 



I have examined a great number of specimens from 

 various localities, taken at different times of the year, — 

 some dozen specimens from Cornwall,* and several from 

 unknown localities in various collections ; some from 

 Ireland, from the Shetland Islands, from Norway, and 

 from near Naples. Every one of these specimens, with 

 the exception of some of the Neapolitan ones, had para- 

 sitic males attached to them : I must also except very 

 young specimens, on which they never occur. On a 

 Cornish specimen, with a capitulum a little more than 

 one fifth of an inch in length, it may be mentioned as 

 unusual that there were three males. In young speci- 

 mens there is generally one male on each scutum, but 

 sometimes there are two, and sometimes none on one 

 side. In large old Cornish specimens I have counted 

 on the two sides together, six, seven, and eight males, 

 and in one Irish specimen no less than ten, seven all 

 close together on one valve and three on the other, but 

 I do not suppose that all these were alive at the same 

 time. In the Neapolitan specimens, however, which are 

 the largest that I have seen, there was in no case more 



* I am greatly indebted to Mr. Peach for liis unwearied kindness in pro- 

 curing me fresh specimens. Mr. W. Thompson allowed me to dissect one, 

 possessing particular interest, out of his three Irish specimens. Professor 

 Forbes procured me a specimen from the Shetland Islands, and Professor 

 Steenstrup was so kind to take pains to send me some Scandinavian 

 specimens. 



