400 The Lobster; Its Structure and History. [July, 
arises a nerve, the two uniting in front of the stomach and giving 
rise to the sympathetic nerve. From the infra-cesophageal gan- 
glion arise the nerves which go to the mouth parts. The thoracic 
ganglia are connected by two commissures, the abdominal by a 
single cord. The sternal artery passes between the commissures, 
uniting the third and fourth thoracic. ganglia. There is no gan- 
glion for the telson. 
The only senses which are localized in the lobster are sight 
and hearing. The position of the eyes has been noticed ; the ear 
is found as a small sac in the base of the antennule. 
Space will allow but a slight account of the development ; for 
details the reader is referred to the papers of Mr. S. I. Smith, 
in Verrill and Smith’s Report on the Invertebrata of Vineyard 
Sound, and in the Transactions of the Connecticut Academy of 
Science. (See also the NATURALIST, July, 1874.) The eggs 
are of a dark green color, and are found from April to November 
on the coast of New England. The embryo in the egg has its 
eyes sessile, its antenne are simple sacs, and its abdominal feet 
are wanting. In the first stage after leaving the egg the thoracic 
feet are furnished with an endopodite fringed with hairs. The 
animals then swim on the surface. In the second stage some of 
the abdominal appendages appear. In the third it loses its ex- 
opodites, and begins to resemble the adult. Specimens three 
inches long have been found with nearly all the characters of the 
adult. During the first year the molts are quite frequent, but 
afterwards they are believed to occur but once a year. The car- 
apace splits down the back, and through the opening the animal 
withdraws itself, leaving its cesophagus and stomach within the 
cast-off skin, and in a few days the new skin becomes hardened. 
EXPLANATION OF PLATES V. AND VI. 
Plate V. Fig. 1, carapace; 2-8, abdominal segments ; 2’, side view of the first ab- 
dominal somite of male; 9, antennule; 10, antennx; 11, mandibles; 12, 15, mar 
illæ; 14-16, maxillipeds ; 17, big pincer; 18-21, remaining thoracic feet; 22, front 
view of third abdominal segment ; 23, transverse section through the carapace. 
Plate VI. Fig. 1, dorsal view, part of the carapace removed, giving & pny 
ee | 
nervous system; 3, diagramatic figure of the circulation (from Gegenbauer) ; he, er 
bryo in the egg (from Smith) ; 5, first stage of young (from Smith). g gills 
s : i 
n, nerve; p, protopodite; p. a, posterior artery; p. c, pericardium ; r, T a 
8, stomach ; t, ovary or testes ; v. a, ventral artery ; s. a, sternal artery: Y. 5 Y 
` Sinus; x, extensor muscles. ‘ 
