194 BULLETIN OF THE BUREAU OF FISHERIES. 
the present time. It is necessary to come to the year 1846 to find a naturalist who 
has taken for the subject of his observations thismollusk so unfortunately celebrated.” 
Since the appearance of this memoir of Quatrefages no detailed account of the 
whole organization of Teredo has appeared. Only in comparative treatises has it 
been taken up. The principal of these are the papers by Grobben (1888), on the 
pericardial glands in lamellibranchs; by Menegaux (1889), on the circulatory system 
in lamellibranchs, and by Pelseneer (1891), in his extensive comparative studies in 
the group. Grobben first observed the anterior adductor muscle in Teredo and 
proved the Teredinide to be dimyarians. Aside from this point, the figure of Teredo 
that he gives is wholly unreliable. Menegaux attempted to establish the homol- 
ogies of the aorte, and Pelseneer described the visceral ganglion and related strue- 
tures. I shall have occasion to refer to these papers in special parts later, and it 
will be seen that the comparative method of study is not always satisfactory if the 
examination of the different forms be not made with sufficient thoroughness. My 
results differ from all of these. Unfortunately, the first two authors do not state 
the species on which their observations were made, and so I can not state that where 
my observations differ from theirs they were in error. There is, however, such 
great uniformity of organization in the various species that we may expect only 
differences in detail. 
My observations have been based chiefly on Xylotrya gouldi Bartsch, and 
in the present paper except where otherwise stated this is the form described and 
figured. I have had specimens in all stages of development from the newly attached 
larva to the adult. I have also studied Teredo dilatata Stimpson and T. navalis 
Linneus, and these have been used where they are essentially different or more 
favorable for description. 
The object of my study of the ship-worms has been twofold. In the first place, 
T have endeavored, by the use of modern methods, to make a detailed study of the 
organization of this highly specialized lamellibranch and to correct some errors 
that have heretofore existed in the descriptions of it. In the second place, by the 
study of young stages, I have been able to trace the transformation of the typical 
lamellibranch larva into the very highly specialized ship-worm. 
I have also traced the early embryology with the artificially fertilized eggs of 
X. gouldi and T. dilatata, in both of which the eggs are laid free into the water. 
Stages later than the typical early lamellibranch veliger, raised in aquaria, I have 
not been able to observe. The intermediate stages, between these and the newly 
attached larva, 1 hope to observe on the larvee of some viviparous species at a 
future time, so as to complete my study of the development from the egg to the 
adult. 
Methods of preserving material—My preserved material was collected and 
prepared for study as follows: By hanging boxes and other structures of wood in 
the water at Beaufort, I was able to obtain all stages, from the newly attached 
larve to ship-worms 4 inches long, with adult organization. The youngest 
stages were collected from the surface of the wood. Later stages were dissected 
out of the wood into which they had bored. Early stages were narcotized with 
cocaine and afterwards fixed with mercuric chloride. Specimens 1 cm. or more mm 
length were treated as follows: They were exposed quickly in their burrows and 
