PENTACRINUS THE YOUNG OF COMATULA. 185 



found, having the membranous expansions inside each 

 of the pinnae considerably extended, at least as far as 

 the fifteenth or twentieth pair ; these, called concepta- 

 cula, at length show themselves distended with ova, 

 which in July, and even earlier, make their exit 

 through a round aperture on the side of each con- 

 ceptaculum, still however adhering together in a 

 roundish cluster, consisting of about a hundred eggs. 

 By what means these ova are dispersed, or how they 

 become attached to the stems and branches of coral- 

 lines, remains to be discovered ; but it is strongly to 

 be suspected that the animal is gifted with the power 

 of placing them in appropriate situations, otherwise 

 we should find them on fuci, shells, stones and other 

 foreign bodies, which does not appear to be the case*. 

 However this may be, the ovum from which the 

 Pentacrinus is developed is first met with in the form 

 of a flattened oval disc, by which it is permanently 

 fixed to the point selected, and giving origin to an 

 obscurely jointed stem that ends in a club-shaped 

 head (PL III. fig. 8), whereon may be observed the 

 incipient formation of the arms and the mouth with 

 its tentacula. At d in the same figure is another, 

 somewhat more advanced, in which the jointings of 

 the arms become more obvious ; whilst at c, the head 

 of the Pentacrinus, completely formed, is ready to 

 separate from the stem that supports it, and thus be- 

 come a detached and roving Comatula. 



* The stalked young are not found only on corallines, as 

 Mr. J. V. Thompson supposed. Mr. W. Thompson finds them 

 on the leaves of Fuci, and remarks that they are very active 

 animals on their pedicles. Forbes 's British Star-Jishes. 



