On the Sexual Characters of the Family of Natades. 117 
the abdomen, the connecting integument was found to be hollow, 
and nothing resisted a flexible probe in passing through from one to 
the other. ‘This operation was performed with great care, with the 
tender and soft end of a spear of grass drawn from a green plant. 
But there was no appearance of the entrails of one,, having come in 
contact with those of the other, for the integument was less than one 
tenth of an inch in its whole thickness, and in length from the body 
or trunk, of one fish to the other, it was three tenths, and in the 
water, when the largest fish was in its natural position, the small one 
could, by the length and pliancy of this skin, swim in nearly the same 
position. It was not ascertained whether, they were of different sex- 
es, or of the same. 
When these fish came into existence it is probable they were of 
almost equal size and strength, but one ‘born to better fortune,” 
or exercising more ingenuity and industry, than the other, gained a 
trifling ascendency, which he improved to increase the disparity, and 
by pushing his extended mouth in advance of the other, seized the 
choicest and most of the food for himself. Yet though he probably ha- 
ted the incumbrance of his companion, and wished the “ marriage 
tte cut asunder,” he afforded protection to his ‘‘ weaker half,” and 
could not eat at without swallowing himself. 
Fort Johnston, N. C., Dec., 7, 1833. 
Arr. XXI.—Observations on the Secual Characters of the Ani- 
mals belonging to Lamarck’s family of Naiades; by Jarep P. 
Kirtianp, M. D. 
Tus interesting family, has of late, received an accession to its 
attractions, as well as numbers, by the discovery of many undescri- 
bed species, in different parts of the world, particularly in the rivers 
and lakes of the United States. 
In consequence of the characters, which are employed for scien- 
tific arrangement, in the systems of conchology, being derived, ex- 
clusively from the shells, the animals seem in a measure, to have 
been disregarded. ‘Their general anatomical structure is not well 
understood: much less the intricate, and minute conformation of their 
sexual organs. It is a disputed point, whether, they are androgy- 
nous, or whether, they possess distinct sexes. 
Mr. Say, in the second No. of the American Conchology, under the 
article Anodonta, remarks, that “ the principal naturalists and anato- 
