32 EDGAR DAVIDSON CONGDON. 



The comparison of a mixed cluster with these suggests strongly 

 that the distal parts of their pedicels are homologous to hydranths 

 and the proximal part to hydranth pedicels. A mixed cluster 

 consists of a hydranth body bearing streptospadiceous gono- 

 phores and its pedicel bearing orthospadiceous gonophores. If 

 its hydranth becomes reduced to a pedicel and its gonophores 

 are simplified to the orthospadiceous condition we will have a 

 structure corresponding exactly to the double orthospadiceous 

 cluster described above both in form and number of parts. The 

 division between the proximal and distal group has disappeared 

 in half of the large clusters. It would be mere speculation to 

 homologize the small clusters with the double ones. If the 

 distal orthospadiceous gonophores of the clusters arose from the 

 streptospadiceous type it seems further probable that the ortho- 

 spadiceous gonophores on the pedicel arose .from streptospadi- 

 ceous pedicel-gonophores which in their turn are phylogenetically 

 younger than those on the hydranth body. 



GENERAL MORPHOLOGY OF EUDENDRIUM HARGITTI. 

 The hydranths are of a bright reddish-brown, the stem of 

 varying shades of brown. Stem unfascicled, colony twenty to 

 fifty millimeters long, becoming nearly transparent near the ex- 

 tremities. Branches straight, few, nearly parallel to the main 

 stem, distributed irregularly, joining the stem by an abrupt bend. 

 Annulations at base of colony and branches, occasionally else- 

 where. Hydranth most deeply colored at base of hypostome, 

 tentacles from thirty-five to forty-five, in contraction forming two 

 closely appressed rows, hypostome very mobile, contracting into 

 a shallow cup or extending to a length greater than the hydranth 

 body. Some hydranths provided with a groove near their base 

 containing gland and thread cells.. 



HISTOLOGY. 



The majority of the histological details of this hydroid corre- 

 spond with descriptions of other forms contributed by various 

 authors. There are, notwithstanding, a sufficient number of 

 unique conditions to make a general review not without value. 



