TROCHOrflORE OF HYDIJOIDKS TINOINATUS (eUPOMATUS). 548 



On the Development and Structure of the Tro- 

 chophore of Hydroides uncinatus (Eupo- 

 matus). 



By 



C;r«"s«*« t'll Sliearer, RI.A., 



Trinitv Colle^-e. Cainl)riclg;e. 



1. IXTHODUCTIUK. 



While working at Naples some years agO; I was led to 

 investigate the earl}' development of the Annelid Eupomatus 

 Avith a view to determining the origin of the mesoblast bauds 

 and their relation to the head-kidneys. This species is 

 common at Naples and breeds throughout the year. The 

 blastahe and gastrulte are very hardy, aud development is 

 normal under the adverse conditions of heat and impure sea- 

 water incidental to their study under laboratory conditions. 

 Fertilisation takes place quickly when the ripe generative 



