( 661 ) 



to be found in Sc. Sk'arn.ti. I noted, liowever, that tliat part of the 

 sac or mantle, which unites the two scuta behind or beneatii the 

 adductor muscle and which can be better seen by moving the two 

 scuta slightly from one another, in the largest and oldest specimen 

 of the collection, showed a crusty and grainy surface — just as if 

 a Flustra or other Bryozoon were attached to it. Investigating a part 

 of that crusty covering I easily found that each grain represented 

 a male and that over a hundred of these were attached to the same 

 female. Each male is inclosed in a kind of capsule (a thickening of 

 the mantle) and that part of the mantle-surface which is opposite 

 the head-end with the prehensile antennae forms a little elevation 

 over the surface of the capsule. They are in parts so closely 

 placed as to flatten one another mutually. Their dimensions are 

 0.7 X 0.5 mm. — they are even small for males of ScalpeUum. 

 Their structure agrees with that of the males of several other species 

 of this genus : round about the opening of the mantle, at the extremity 

 of the little elevation over the surface of the chitinous capsule, four 

 rudimentary valves are observed. What I think, so far as my experience 

 goes, is characteristic for this species, is that short rudimentary 

 tentacles are attached to the surface of the mantle between (alternating 

 with) the small valves, little appendages — -which of course have 

 nothing in common with the articulated antennae or other limbs of 

 the Cirripedes. Should any doubt remain, as to whether these little 

 parasites really represented the males of this species, these tentacles 

 might be used to dissipate it. A few small, quite young females, in 

 which the capitulum however was already furnished with calcareous 

 valves and the whole appearance of which corresponded with an 

 early condition of fullgrown females, were found attached to the 

 surface of the capitulum of one of the large specimens. Now, these 

 little females are furnished with the same tentacles. They are 

 embryological organs, which of course may have importance from a 

 morphological or phylogenetic point of view^ but Avhich have dis- 

 appeared in the fullgrown females. In the young females they occupy 

 the same place as in the males, viz. at the free extremity (the tip) 

 of the capitulum attached to the chitinous surface between the two 

 calcareous plates which represent the terga, near the anterior extremity 

 of the orifice — in the females large, in the males relatively much 

 smaller — which gives entrance to the cavity in which the animal's 

 body is lodged. 



I do not believe that examples are know^n in animals so highly 

 developed as Cirripedia of such a pronounced polyandry as in this 

 species of ScalpeUum. As a rule, the number of males found attached 



46 



Proceedings Royal Acad. Amsterdam. Vol VIII. 



