BIOLOGICAL STUDY OF TAP WATER. 423: 
of the circumference, and on the opposite side of the inner cyst there 
is a similar projection. Stein figures these as occurring about the 
same place on both cysts, but in all that I observed they were on 
opposite sides, and on the outer cyst there was only one. The 
diameter of the outer cyst in several instances was found to be about 
0.0155 mm,, and through the protuberance 0.0217 mm. ; and of the 
inner 0.0124 mm. Figs. 5, 6. 
Dinobryon stipitatum, Stein, was also present once or twice. This 
species differs from the one just described in the greater proportionate 
length of the loricae, which are trumpet-shaped, widest at the mouth, 
and tapering off into the acuminately pointed posterior end, being 
about 7 or 8 times as long as their greatest breadth. The zooids 
very much resemble those of D. sertularia, but are more elongated, 
and occupy the anterior half of the lorica, being attached by a 
thread-like ligament to its lower side wall. A large amylaceous 
more or less spheroidal body is situated near the posterior part of 
the endoplasm. The length of the lorica according to Kent is 335”. 
Two or three other species of Flagellata have also been seen, 
though rarely. 
One, belonging to the Choano-Flagellata, i.e., monads with a collar 
surrounding the single flagellum, I have referred to Salpingoeca 
Susiformis, Kent. Kent gives the following characters for this 
species: ‘* Lorica sessile, sub-fusiform, or vase-shaped, widest cen- 
trally, tapering equally towards the two extremities, but expanding 
again anteriorly into a somewhat prolonged and everted neck ; con- 
tained animalcule flask-shaped as in S. amphoridiwm, J. Clark, but 
of larger size. Length of lorica yg55”._ Hab., fresh water, solitary.” 
This form was seen only on one occasion, attached to a frond of 
Rhizosolenia Eriensis. The lorica was empty and corresponded 
closely with the above description. In another part of the field 
however I found what probably was the zooid of this species which 
had been set free, though it is possible that it might have been 
Monosiga socialis, Kent, with the description of which it closely 
agreed. The body was somewhat pyriform, widest posteriorly, with 
no pedicle ; a single Jong flagellum surrounded by a collar. Length 
of the body 0:0062 mm. (= qo00"), breadth 0:00465 mm. (= sad00")- 
On one occasion I got a glimpse of a colony which I think belonged 
to the family Codonosigidae of this order. Unfortunately I lost 
