270 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



bers of houses in Jamestown have been fairly gutted by them 

 doors, window-sashes, floors, and roofs all being eaten up, 

 leaving nothing but the bare walls. Letter. 



SPREAD OP THE CABBAGE BUTTERFLY. 



According to Dr. Uhler, of Baltimore, the European cab- 

 bage butterfly (Pontia brassicce), the pest of the agriculturist, 

 has reached Baltimore in its invasion of the United States. 

 It has been known for some years more to the eastward, and 

 has been slowly but surely creeping along, until it bids fair 

 to involve the whole country in its ravages. Letter from 

 Dr. Uhler. 



OYSTER BEDS OF GERMANY. 



Professors Mdbius and Hensen have been lately engaged 

 in a careful investigation of the condition of the oyster beds 

 of Schleswig, and have ascertained that a full-grown oyster 

 can produce a million of young in a single season. They also 

 ascertained that the Schleswis: ovsters at least have no de- 

 cided manifestation of sex during the winter, but that, prior 

 to the breeding season, in some the cells of the generative 

 glands develop spermatozoa, while others develop only eggs, 

 the numbers in the two divisions being about equal. This 

 sexual development is later in the deeper beds than in the 

 more superficial ones, probably because the stimulus of in- 

 creasing heat acts earlier at shallow depths than at greater 

 ones. They also found reason to believe that the egg-bear- 

 ing generative glands, after discharging their eggs, appear 

 to have spermatozoa to form in them. 19 C, October 21, 1871, 

 xlii., 344. 



enemies of oyster spat. 



According to Mr. Buckland, among other enemies of young 

 oysters in the English breeding parks or ponds are certain 

 small fish, such as the gobies, sticklebacks, etc., which devour 

 the spat with intense relish. lie finds in these minute ene- 

 mies the reason why such poor success has attended many of 

 the experiments in oyster breeding, and advises that some 

 fish be introduced especially addicted to destroying the 

 young fish fry in question. A comparatively small number 

 of young bluefish would probably very soon exterminate 



