Three Pacific Species of {Including a New Species)^ 
Their Hosts ^ Medusae, and Relationships. 
(Coelenterata, Hydrozoa)^ 
Cadet Hand^ 
The hydroid "ear,” which lives as a com- 
mensal upon the tubes of sabellid polychaetes, 
has been described from the Atlantic by Gosse 
(1857) and from the Pacific by Uchida and 
Okuda (1941) and by Hand and Hendrickson 
( 1950 ). Hincks (1872) noted that the medusae 
produced by Lar sabellarum Gosse were sim- 
ilar to Willia stellata Forbes, and later Browne 
(1896) clearly established that the medusa of 
Lar sabellarum was Willia stellata. Uchida and 
Okuda ( 1941 ), in their study of the Japanese 
"Lar,” showed that their hydroid was that of 
the medusa Proboscidactyla flavicirrata Brandt 
and, as a result of their study together with 
the data of Browne and Kramp (1939), united 
the genera Willia and Proboscidactyla, retaining 
the name Proboscidactyla because of priority. 
Hand and Hendrickson (1950) described a 
new "Lar,” Proboscidactyla sp., from California 
and suggested it might be the hydroid of the 
medusa Proboscidactyla occidentalis (Fewkes). 
Since 1950 the author has had an opportunity 
to examine medusae of Proboscidactyla from 
off the coast of Oregon, Monterey Bay, near 
Santa Cruz Island, and the San Diego region, 
the latter three localities all being in California 
waters. It also has been possible to obtain 
specimens of "Lar” from Puget Sound (Wash- 
ington) and La Jolla, California. An examina- 
tion of the hydroids and medusae has shown 
that three separate species of Proboscidactyla 
occur on the Pacific coast of the United States, 
a northern species (P. flavicirrata) , a central 
^ Contribution from the Scripps Institution of 
Oceanography, New Series No. 668. Manuscript re- 
ceived February 20, 1953. 
^ Scripps Institution of Oceanography, University 
of California, La Jolla, California. 
species {Proboscidactyla sp. of Hand and Hen- 
drickson 1950 , named for the first time in the 
present report), and a southern species, P. 
occidentalis. 
The definition of species in the Hydrozoa, 
more especially among the gymnoblasts, has 
long been based on rather gross, frequently 
ephemeral, characters such as size, shape, 
number and type of tentacles, arrangement 
of hydrorhizae, and the kinds of individuals 
present in the colony. In the following report, 
a not completely proved hypothesis has been 
used as one of the primary criteria of vyhat 
is to be taken as a species. This concerns the 
nematocysts, and, briefly stated, the hypo- 
thesis is that each species of coelenterate can 
be identified by its possession of a unique 
group of nematocysts (the cnidom), at least 
with regard to size and shape, although not 
necessarily with regard to kind. This hypo- 
thesis has stemmed from the work of Weill 
( 1934 ) and has proved acceptable for sea ane- 
mones as demonstrated by the numerous 
studies of Dr. Carlgren of Lund, Sweden. The 
work of E. G. Papenfuss (1936') on scypho- 
medusae and of F. S. Russell (1938) on hydro- 
medusae lends much validity to the contention. 
To date no refutation of this hypothesis has 
been presented, and the study of the species 
of "Lar” demonstrates the further usefulness 
of nematocysts in the identification of hy- 
droids. The terminology of nematocysts used 
herein is that of Weill (1934). 
It will be noted in the following pages that 
the nematocysts of the hydroid stages are very 
similar from species to species. This, perhaps, 
is not unexpected as hydroids are immature 
51 
