Vol.i.] Tor fry . — Hydroida of the Pari fie Const. 43 



of root filaments, the only respects in which they differ conspicu- 

 ously. It is because of the transitional condition of these 

 filaments in such forms as Tubularia couthouyi that we are able 

 confidently to interpret those of Corymorpha as homologous with 

 the creeping hydrorhiza of other forms. 



It maybe mentioned that peripheral canals and a solid endo- 

 dernial axis are present in T. couthouyi and T. indivisa, as well 

 as in Corymorpha . This condition seems to be a direct adapta- 

 tion to size, since all three species have exceptionally large 

 diameters. 



Tubularia Linn. 



Trophosome. Hydroeaulus usually unbranehed and rising from a 

 creeping hydrorhiza; both completely invested with perisarc. Hydranth 

 with two sets of filiform tentacles. 



Gonosome. Gonophores fixed, more or less medusoid. 



Tubularia crocea (Ag.). 



PI. II. Figs. 22, 23. 



Parypha crocea, Agassiz, Contr. N. H. U. S., IV, 1862. 

 Parypha microcephala, A. Agassiz, 111. Cat., II, 1865. 

 Tubularia crocea, (Ag.), Allman, Gymn. Hydr., 1871. 



Distribution. San Francisco Bay, San Pedro Harbor, San 

 Diego Bay, Cal. Eastern U. S. (Ag.). 



This species is essentially a brackish water, harbor form. It 

 has been recorded already for San Francisco, Cal., by Alex. 

 Agassiz, in his Illustrated Catalogue ('65) under the name of 

 Parypha microcephala. Agassiz distinguished it from P. crocea 

 in the belief that it had a more slender stem and smaller head. 

 Numerous observations on the living animals from Oakland 

 Harbor, at different times of the year, have demonstrated to me 

 that these characters are not constant; and I cannot find any 

 others upon which to base a separation of the western from 

 the eastern form. According to observations made at San Pedro 

 during December, on living animals, the tentacular processes on 

 the female gonophores are eight iu number, though they may 

 vary greatly in size and shape, appearing at times as little more 

 than small welts about the bell mouth. L. Agassiz says of the 

 male gonophores: "The male medusoids never have any tenta- 

 cles, nor do they deviate from an almost perfectly spherical 



