232 SCALPELLUM VULGARE, 



resolved to look with care at these parasites ; on doing 

 so, I soon discovered that they were Cirripedes, for I 

 found that they adhered by cement, and were furnished 

 with prehensile antennae, which latter, I observed with 

 astonishment, agreed in every minute character, and in 

 size, with those of S. vulgare : the importance of this 

 agreement will not at present be fully appreciated. 

 I also found, that these parasites were destitute of a 

 mouth and stomach ; that consequently they were short- 

 lived, but that they reached maturity ; and that all were 

 males. Subsequently the five other species of the genus 

 Scalpellum were found to present more or less closely 

 analogous phenomena. These facts, together with those 

 given under Ibla (and had it not been for this latter 

 genus, I never probably should have even struck on 

 the right track in my investigation,) appear sufficient to 

 justify me, in provisionally considering the truly wonderful 

 parasites of the several species of Scalpellum, as Males and 

 Complemental Males. When these parasites are fully 

 described, will be the proper time to discuss and weigh 

 the evidence on their sexual relations and nature. I will 

 now describe the parasite of S. vulgare. 



General Appearance. — Shape, flask-like, compressed 

 (PI. V, fig. 9, magnified 36 times), with a short neck : 

 the outline is usually symmetrical, but sometimes is a little 

 distorted on the under side. The creature is imbedded 

 more than half its length or depth in the transparent, 

 spine-bearing chitine border of the scutum of the herma- 

 phrodite. Its length, or longer axis, varies from i^-ths ; 

 its breadth, or transverse axis, is 6 4°o 7 ths ; and its thickness, 

 for it is much flattened, is only ^ths of an inch. On the 

 summit, there is a fimbriated orifice (a), the size of which 

 can rarely be made out quite distinctly, owing to the 

 extreme thinness of the membranous edges. A little 

 way beneath the orifice, there are four little blunt, bristly 

 points (b), generally rather more than the ^th of an inch 

 in length ; they are rather variable in size, and seem to 

 be of no functional importance ; directly beneath them, 



