Protohydra leuckarti — W IESER 
107 
Fig. 2. Map of distribution of Protohydra leuckarti. 
along the beaches is subject to greater varia- 
tions in salinity due to the inflow of several 
rivers, but it never can be called brackish. 
Therefore, Ekman’s statement (1953: 117) to 
the effect that P. leuckarti is a typical indicator 
of brackish water (that is, mesohaline, from 
3 to lOO/oo) does not hold for this locality. 
The temperature of the water is fairly stable 
the year round, varying from 8.5° in winter 
to 14° in summer. This, of course, applies to 
the central portion of the Sound only. The 
intertidal zone will be subject to greater 
extremes. 
The fauna accompanying P. leuckarti is a 
typical sandfauna with gastrotrichs (Turba- 
nella spp., Macrodasys sp., Paraturbanella sp.), 
cumaceans ( Cumella vulgaris , Lamprops kra- 
sheninikova ), many nematodes, etc. At Vashon 
Island, due to the finer substratum and the 
proximity of seaweeds, some representatives 
of a mud-fauna, e.g., Corophium insidiosum and 
Leptochelia dubia , occurred in the same habitat. 
My specimens of P. leuckarti conform with 
previous descriptions. This is especially evi- 
dent if the structure and size of the nemato- 
cysts, as shown in Figure 1 c, d, are compared 
with the figures and data by Luther (1923), 
and Weill (1934). 
In length the adult specimens varied be- 
tween 0.7 and 2 mm., according to the state 
of contraction of the animal. 
I have encountered copepods and nema- 
todes in the body cavity of some of my spe- 
cies. Others were actually seen feeding on 
nematodes. In one case a Protohydra had 
begun to swallow a nematode about five 
times the length of the hydrozoan. By its 
violent movements the nematode had pierced 
the posterior end of its predator so that the 
latter appeared to be pulled like a sleeve over 
the prey. The body of the nematode was 
