PROCEEDINGS OF SCIENTIFIC SOCIETIES. . 165 
cutta, that a certain species of fish destroyed this worm, and only those 
who gogi in tanks unstocked with this fish were troubled by them. 
Mr. W. Winwood Reade said, that in Africa they were much more 
common in Guinea proper, than on any other part of the coast; it w 
there generally believed to be prevalent on account of the impurity = 
the drinking water. 
Mr. Theodore Lyman remarked on the laws of breeding Shad and 
Salmon, the gradual extirpation of these fish from our rivers by the 
erection of dams, and exhibited models of fish-ways which had recently 
been constructed on the Merrimac, under the direction of the State 
Commissioners. 
Mr. F. W. Putnam, after announcing the donation of two species of 
fish from Lake Witch gee one the Lota maculosa (Ling, or fresh- 
water Cusk), and the other a species of Lake Trout, probably the Sal- 
mo confinis of De Kay, remarked that it seemed to of 
doubt whether many of our Lake Trout are anything more than forms 
of the Brook Trout. Referring also to Mr. Lyman’s remarks on the 
habits of the Salmon, Mr. Putnam stated that Dr. Bernard Gilpin, of 
Nova Scotia, had recently been making observations upon the male 
Salmon, and had discovered that it must have three sets of teeth form- 
ed one after the other; that one set falls out just before ascending the 
river, when the ca cartilaginous enlargement of the jaws takes place; that 
a new set grows out durin g the ascent of the stream, which is de- 
Stroyed during its contests iti others of its sex, and by excavating 
` hollows in the gravel for the eggs; in this condition it returns to the 
sea, where it again attains a new and normal set of teeth. 
upon a recent gathering of Diatomaceous mud, from Pleasant Beach, 
Cohasset, 
B. J. Jeffries exhibited some glasses and metallic mirrors used 
in examination of diseases of the eye. He made remarks upon the use 
of colored glasses (b blue), the mode of coloring, and the advantage of 
this particular color (cobalt blue) over green or grey in relieving the 
eye from the effects of sunlight. 
INSTITUTE, Salem, February 4.—Mr. F. W. Putnam exhib- 
ited a singular specimen of the Horned Pot (Pimelodus atrarius 
De Kay) from Lake Champlain, presented by Dr. B. Pickman, of Bos- 
ton. The fish was pure white, thus showing that albinos occur among 
as well as in the birds and mammals, though this was the frst 
instance of albinism known to him as occurring in this class. 
