Notes on the genus Microcotyle. 17 
all the worms this presents the appearance seen in the drawing, — 
an oval or nearly spherical bulbous mass covered over with minute 
spines which point backward and extend into the eversible small 
orifice which forms the outlet for the uterus. Behind this there is 
a second aperture for the small conical ceirrus-like end of the vas 
deferens. This is guarded on each side by an elongated group of 
about ten or twelve similar short spines. 
The ovary is a somewhat indefinite elongated sac crossing the 
middle of the body and extending backward. — Its oviduct receives 
the channel from the clearly defined seminal reservoir and that from 
the vitelline duct and passes through the shell gland into the straight 
uterus. 
The vaginal orifice is median and dorsal and the vagina divides 
some distance behind this to join the vitelline duets which run back 
laterally receiving branches from the vitellarium to reunite in 
forming the vitelline reservoir which sends its duct to join the 
oviduct. 
The eggs, one or two in number, are provided posteriorly with 
a rather stout tapering prolongation, anteriorly with a similar 
structure which is elongated, however, into a very long and delicate 
tangled and coiled filament. The testes vary in number from eighteen 
to twentyseven and send as usual the undulating vas deferens through 
the mid line of the body forward to the genital opening. 
Measurements. 
Length 3,5—4,5 mm 
Width 0,6—0,7 
Length of sucker disc 7—1,0 
Suckers 50—78 
Size of Suckers 0,30xX 0,2 
Eggs 0,12%X.0,08 
Testes 18—27 
New York Aquarium. 
Many of the fish belonging to the families Chaetodontidae, 
Sparidae and Haemulidae which I have obtained from the New York 
Aquarium have been found infected with the Microcotyle just described. 
So severe is this infection that it may be said to have been the 
cause of death in many instances especially in the Chaetodontidae 
where it is almost universal. 
