78 HAROLD HEATH. 



while a third frequently makes its appearance in the vicinity of 

 the hydrorhiza about the time the first medusa is liberati-d. 

 Beyond this point the order of development is not known, Inn 

 Fig. 2 illustrates a few of several different stages. The mode of 

 development of the medusa is typical, and results in a bi-tentacu- 

 late type. 



With the exception of the distal portion of each hydranth, 

 including the tentacles, the entire colony is ensheathed in a cuticle 

 often coated with minute organisms and sediment. In the older 

 portions this investment is comparatively firm with the exception 

 of that surrounding the hydranths, which is less dense and more 

 flexible. The medusa buds are likewise covered, and for a time 

 prior to their detachment are bound to the stem by an irregular 

 cuticular bridge. 



In the younger hydranths the line of demarcation between 

 them and the stem is not clearly defined, but as they become older 

 the boundary is more distinct, the hydranth growing more 

 globular owing, to some extent at least, to the greater height of 

 the endoderm. In the younger stages each hydranth bears four 

 tentacles, later four others appear, often with slight irregularities 

 in the time intervals, and finally with the appearance of four more 

 the number is complete. 



The following diagnosis will distinguish the present species 

 from other known forms: Perigonimus pugetensis new species, 

 twelve tentacles. Hydranths arising invariably from the hydro- 

 rhiza, and bearing as many as four scattered bi-tentaculate 

 medusa?. Cuticle relatively thin. Occurs on the agonoid ii>h, 

 Hypsagonus qiiadricornis, in Puget Sound, Washington. 



