Vor. 2] Torrey—Hydroids of the San Diego Region. pa 
Both the erect and creeping forms were found at San Diego. 
Overgrown with C. hinckst. No gonosome, June 29, July 15, 
1903. : 
Fam. SERTULARIIDAE. 
Anyone who has had oceasion to work among the Sertulariidae 
will admire the masterly way in which Nutting ( :04) has dealt 
with the perplexing questions of classification in that family. I 
am not yet prepared, however, to abandon Schneider’s plan of 
segregating the species into typical groups which shall take the 
places of genera. These groups do not necessarily give their 
names to the species which they include. Thus they discourage 
the growth of synonyms, offer no awkward bars to the free pass- 
age of any species from one group to nearer relatives, and at the 
same time lessen the confusion which the present unsettled state 
of opinion regarding the relationships of existing species tends to 
produce. 
When it is not easy to define groups clearly, owing either to 
the uncertain values of diagnostic characters or to baffling tran- 
sitional forms, it is plainly desirable to have as few groups as 
convenience will permit. Marktanner-Turnerestcher (790) dis- 
tinguished 18 genera. Nutting has reduced this unusual total 
to 12; but that number, I am convineed, is still too large. The 
distinetion between Thuwiaria and Abietinaria hardly seems of 
enough service to overweigh the practical difficulties which it 
invites; and although Nutting has put forth every effort to make 
it useful, he has only succeeded in distinguishing the genera by 
relying now on one, now on another combination of characters, 
not an attractive makeshift. But however desirable or undesir- 
able this procedure may be, I make no reservations in condemn- 
ing Allman’s genera Thecocladium and Synthecium as Nutting 
has defined them. According to Allman, 7hecocladium is distin- 
euishable by the intrathecal origin of its branches, Synthecium 
by the intrathecal origin of its gonangia. The justice of my 
objections ( :02, pp. 61, 62) to genera founded on single charac- 
ters of such a sort is admitted by Nutting, who then attempts 
to strengthen both genera, but particularly Syntheciwm, which 
alone ocurs in American waters, by supporting them on combi- 
nations of characters. Syntheciwm is accordingly based upon a 
