ZOOLOGY. 337 



upon eels, and who are notoriously healthy. In. describing- the man- 

 ner of generation of eels, the author says, " Every year in the month 

 of March or April, there appear at the mouths of ail the rivers, just at 

 nightfall, myriads of transparent filiform animalcules from six to seven 

 centimetres long, which raise themselves to the surface of the water in 

 compact masses, and ascend the streams. These animalcules are 

 nothing but newly hatched eels, leaving their birthplace to disperse 

 themselves throughout the canals, lakes, and brooks, which communi- 

 cate with the rivers." The quantity of these animalcules is sufficient 

 to fill all the waters on the globe, and if transported to basins prepared 

 to receive them they would furnish an inexhaustible supply of food. 



Preoccupied with this idea, the author caused a quantity of these 

 animalcules to be brought alive to the college of France, and placed 

 in large wooden vats. The young eels were then from six to seven 

 centimetres long, and one centimetre in circumference around the 

 largest part of the body. After remaining seven months in the vat, 

 they were twelve centimetres long, and two centimetres and two mil- 

 limetres in circumference ; at the age of eighteen months, twenty-two 

 centimetres long, four centimetres and eight millimetres in circumfer- 

 ence ; at the age of twenty-eight, thirty-three centimetres long, and 

 seven in circumference. Thus, though placed in very small basins, 

 the eels grew from eight to ten centimetres in length, and two and a 

 half in circumference, every nine months. 



THE AMERICAN PORPOISE A NEW SPECIES. 



AT a meeting of the Boston Society of Natural Plistory in January, 

 Prof. Agassiz stated that the common porpoise of our waters, which 

 has generally been regarded as identical with the Phococna communis 

 of Europe, proves upon examination to be a distinct and hitherto un- 

 described species. In P. communis the temporal groove of the skull 

 is narrow and oblong ; in the American species it is as wide as long. 

 The general form of the skull is also different. In the European spe- 

 cies the posterior surface is nearly vertical, in the American it is much 

 curved. The teeth of the American species, although agreeing in 

 general with those of the European in form, are grooved on the broad 

 faces near the summit so as nearly to divide them into three lobes; in 

 the European they are smooth. The dorsal fin is serrated and fur- 

 nished with very characteristic tubercles in the American species, 

 which are not mentioned in the descriptions of P. communis. Prof. 

 Agassiz proposes as a name for this new species that of P. Ameri- 

 cana. 



CAUSE OF THE JET FROM THE BLOW-HOLES OF WHALES. 



AT a meeting of the Boston Society of Natural History, in Feb- 

 ruary, Dr. Wyman made some remarks on the probable cause of the 

 jet from the blow-holes of whales. While on a recent visit to Labra- 

 dor, he had had an opportunity of observing this phenomena. Three 

 causes for this jet had been assigned, namely, the water taken into 



