16 Verm . 
VEKMES. 
as to their infection of Ophiuricls , and the characters of the different 
forms. 
Whitman (32) subjects the statements of Van Beneden to a searching 
criticism, and thinks that only 2 genera are to be distinguished as yet in 
the Dicyemidce — Dicyema, and Dicyemmenea. He thinks that Julin has 
really proved the existence of a mesoderm, and he believes that the 
group is one which has been degraded by the parasitic habit ; whether 
they are derived from such a form as Dinophilus or from the Trematoda, 
further investigations must decide. Nematogenic individuals are found 
in young, and rhombogenic in old Cephalopods ; so that the parasite 
appears to differ with the age of its host. 
