ANATOMY OF SUTROA ROSTRATA. 4 
sentation of the same. I generally found three eggs or young worms in the 
sapsule. 
The worms appear fully developed in July and August, at which time I 
found mature specimens. In May only immature ones were found, but as some 
of those were quite small it is likely that the worms remain mature for a long 
period, and that perhaps the proper breeding season is during the winter months. 
In size and form Sutroa rostrata much resembles Rhynchelmis limosella, Hoflin. 
Mature specimen reach a length of three inches and a width of one-eighth of an 
inch, but generally are considerably smaller. The form is also similar to that of 
the above worm, The body is round or quadilateral; in many specimens the sides 
are even concave (Fig. 3). The posterior part of the body is again very much flat- 
tened out, quite transparent, and so brittle that care is necessary to yet any entire 
specimen. 
The anterior part of the worm, or the cephalic lobe proper, is elongated and 
filiform, its length exceeding the width of the body. This characteristic is 
also found in Rhynchelmis limosella, and indeed so similar are the two worms exte- 
riorly that one may easily be mistaken for the other. Fig. 1 represents a Sutroa, 
nat. size; Fig. 2, the anterior portion of the body; and Fig. 3, a transverse section 
of a quadilateral specimen. 
Vascular System.—The dorsal vessel (Figs. 4 and 5, v. d.) is pulsating. The 
ventral vessel (Wig. 4, v. v.) is not pulsating. In the figures the pulsating vessel is 
represented, red, the non-pulsating one as blue. The ventral and dorsal primary 
vessels are connected in the cephalic lobe. where at the apex one vessel connects 
directly with the other (Fig. 4, I). Between this cephalic plexus and segment 
XIII no direct connection exists between the two primary vessels. But from 
segment XIII toward the posterior end of the body, we find in every one 
a secondary gastric vessel which undoubtedly connects the dorsal and ventral pri- 
mary trunks. 
The dorsal primary vessel (Figs. 4 and 5, d. v.) is entire, not forked, as is 
the case in the other genera of Lumbriculina. In every segment it emits secondary 
vessels, which are of two kinds, gastric and perigastric. The perigastric vessels 
occur in all the segments of the body; the gastric vessels only in the posterior, 
beginning with segment VIII. 
In each of the six anterior segments we find only one pair of perigastrie ves- 
sels, but each vessel shows a distinet forking, less so in segment I, but more dis- 
