No. 2.] A NEW MARINE TRICLAD. 187 
habits, to collect a number of the crabs early in the season and 
to confine them in a large fish-box or similar receptacle. JB. 
propingua appears to breed at the same time as Syncalidium. 
10. General Conclusions. 
In conclusion two questions on which the foregoing anatom- 
ical study of Syxcelidium has a bearing may be wbmery 
discussed. The first relates to the origin of metamerism, the 
second to the systematic position of the three Triclads parasitic 
on Limulus. 
A careful study of the strikingly regular anatomical features 
of Gunda segmentata \ed Lang ('81») to attempt a derivation of 
the Hirudinea from Turbellaria-like forms. Such a derivation 
involves implicite the view that metamerism in the Annelida 
and higher forms is not derived from a process of budding like 
that observed in such forms as Microstomum, but from a con- 
dition like that which obtains in Guwnzda, where the testes, 
vitellaria, gut-diverticula and transverse portions of the nerv- 
ous system have a segmental arrangement. This view has 
many attractions and I was inclined to give it great weight 
when I began my study of Syucwlidium. Here; too,, the 
nervous system has an arrangement quite as regular as that of 
Gunda, and preliminary observation pointed to a pair of gut- 
diverticula, a pair of testes and a pair of vitellaria to each 
transverse and each pair of lateral nerves. But the examina- 
tion of a great number of specimens of all ages soon convinced 
me that the gut-diverticula are very variable in number and 
arrangement, that they are not paired and do not coincide with 
the lateral nerves. The testes and vitellaria accommodate 
themselves closely to the gut-diverticula, and vary correla- 
tively. The water vascular system and musculature, of course, 
showed no signs of metamerism, so that I was left with the 
nervous system as the only apparently metameric organ in the 
body of Syncalidium. Hence, providing Lang’s Fig. 1 is not 
unduly schematized, —and I am not willing to believe this, —I 
am forced to admit that Syacwlidium falls far short of Gunda 
in the metameroid arrangement of its parts. The Limulus 
