REPRODUCTIVE SYSTEM. 99 



total length of ^th : in the longest and best developed 

 specimens of Chthamalus stellatus, the nodular enlargement 

 was much elongated and spindle-shaped, and not above 

 half the diameter it had in the earliest stage ; the posterior 

 filament (measured from the front of the enlargement, this 

 consequently being included) was §^gtH in length, and the 

 front part only ^th, giving a total length of ^ths of an 

 inch. These observations agree pretty well with Kolliker's;* 

 but this author states, that perfectly developed sperma- 

 tozoa are absolutely without any nodular enlargement: if this 

 be the case, I have never chanced to see the spermatozoa in 

 their perfect condition. Mr. Bate, also, figures some (PL 29, 

 fig. 7, c) in this state, without any enlargement. 



The probosciformed penis lies adpressed on the under side 

 of the thorax, with its apex generally projecting between the 

 first and second pairs of cirri. It presents the same ringed or 

 articulated structure as in the Lepadidse : it arises from an 

 unarticulated projection or support, which also forms the 

 posterior border to the anus. This support often terminates, 

 as first observed by Poli, in a very sharp point ; but this 

 point cannot be of much functional importance, for though 

 present in Balamis balanoides, it is absent in the closely 

 allied B. crenatus ; in Tubicinella there is only a rudiment 

 of this point ; I have not observed it in any member of the 

 Chthamalinse. The strong, transverse and longitudinal 

 muscles with which the penis is furnished, are attached to 

 this support. The apex or orifice of the penis is, I believe, 

 invariably surrounded by some bristles. Its length varies 

 much, according to its state of contraction or relaxation; 

 and this again, I believe, is dependent on the condition of the 

 male secreting organs. In a small specimen of Elminius 

 modestus, the penis was actually .thrice as long as the whole 

 thorax, including the prosoma : in Pacltylasma and in Oc- 

 tomeris angulosa, the penis is very short, being equal only 

 to once and a half the length of the pedicel of the sixth 



* 'Annales des Sciences Naturelles,' (2d series), torn, xix, p. 348. Kolliker 

 refers to Wagner's paper on the same subject, in Wiegmann's 'Archiv,' 1835, 

 part ii, pi. iii, fig. 9. He also refers to Von Siebold's observations. Mr. C. 

 Spence Bate has figured, in the ' Annals and Magazine of Natural History' 

 (vol. viii, 2d series, 1851), the spermatozoa of Balanus balanoides, perforatus, 

 and of Verruca {Clilia) Strbmia, and of these I have given copies, PI. 29, fig. 7. 



