“Morse. | 358 [March 19, 
comparisons. Therefore the points to follow, trivial in themselves, 
cannot, with justice, be overlooked in these comparisons. 
Dr. Williams, in his elaborate work on the British Annelida, in 
describing the dissolution of Arenicola and Nais, says in regard to 
the former, that the division occurs somewhere within the middle 
third of the body, though sometimes the head is detached, and some- 
times the tail. This process, both in the Nais and Arenicola, occurs 
in July or August. The cephalic and caudal portions continue for 
some time to writhe in the sand. Towards September the. fragments 
disappear by decomposition, the parts turning black. He further 
says that the sand of the sea-shore, and the water of the fresh water 
pools are thickly strewn with the mutilated bodies of these worms. 
‘Tt is a catastrophe which every fall involves the whole community.” 
He believes therefore that these Annelids are annuals. ‘They are 
born during the latter months of one summer, and survive the win- 
ter, attain the maturity of growth, reproduce the species, and die by 
the spontaneous subdivision of their body into fragments.” 
In studying Lingula pyramidata, I had come to the conclusion that 
with this Brachiopod at least, their duration of life did not probably 
exceed one year. Of over one hundred specimens of Lingula col- 
lected by myself in June, and as many more collected by Dr. Elliott 
Coues in July, I had remarked as a noteworthy fact, that specimens 
varied but little in size. I did not meet with a single young speci- 
men, or, rather, a single small specimen. Furthermore the shells in 
all cases presented the same features of newness. There were no 
erosive or parasitic growths upon them (though late in the fall there 
is no reason why hydroid growth might not ocgur on that portion of 
the shell exposed). This fact, coupled with the absence of even a 
small specimen, for which I particularly searched, led me long ago to 
believe that they were all of the same age, and that their life did not 
exceed one year. 
I brought several specimens home with»me to Salem, Mass., and 
kept them alive during the summer months; imitating as far as pos- 
sible the conditions in which I found them, keeping them in the 
same sand in which they were collected. They all died within a 
few days, during the last of September, and in their death they re- 
peated almost precisely the features described by Dr. Williams in 
Arenicola and Nais. Spontaneous division occurred between the 
thorax and peduncle. The thorax was thrown out on the surface of 
1Report of the Brit. Asso. for Ad. of Sci. 1851, p. 248. 
