6o 



SCIENCE, 



[Vol. XXII. No. 548 



fine adjustment is generally suflScient to teep it constantly in 

 focus, and I have no doubt that it might be adjusted well enough 

 to use satisfactorily as high a power as a long focussed quarter- 

 Inch objective. 



Indeed, the instrument has proven to be all that could have 

 been expected of it as an orienting microscope, and, at the same 

 time, its value for ordinary work is is no way decreased, unless 

 the slightly less rigidity of the stage is an objection. 



Plans have already been completed for a dissecting microscope 

 for use in my laboratory embodying the same principal but in- 

 volving greater changes from instruments now in use. The new 

 stand will consist of a stage which remains horizontal, so that 

 insects may be dissected on it under water. The arm is jointed 

 and the lower section bent so that the axes of the two hinges are 

 at right-angles to each other. There will be the necessary ar- 

 rangements for so adjusting these axes as to make them intersect, 

 and the tube will be fitted with a nose-piece adjustment. 



The base will be clamped to the desk for sake of rigidity. The 

 focussing will be all done at the stage, though the tube will move 

 to accommodate the varying focal-lengths of the objectives. 



It is expected to use the objective under water, providing it 

 with a hard-rubber shield having a cover-glass on the end. This 

 kind of instrument should be also very useful for the study of 

 aquatic forms. 



SUMMER WORK IN MARINE ZOOLOGY AT NEWPORT. 



BT W. E. CASTLE. 



Out on the extreme southwestern point of the Island of Rhode 

 Island, in Narragansett Bay, is Castle Hill, the comfortable resi- 

 dence of Mr. Alexander Agassiz. Against this point the waves of 

 the Atlantic break with full force as they sweep round the east 

 end of Long Island past Point Judith. This is the one rough spot 

 in the trip from New York to Boston by boat. 



As the tide comes in at Castle Hill and passes the narrow en- 

 trance of the bay, it makes a bend and carries its rich pelagic life 

 into a little cove on the north side of the point. On this cove is 

 Mr. Agassiz's laboratory. 



It is a modest-looking little structure, modelled after a Swiss 

 cottage, but within it is a very paradise for the marine zoologist. 



Aquaria, tanks, and glassware it contains in abundance, while 

 fresh and salt water are carried in pipes to all parts of the labora- 

 tory. Fresh, salt water, and air to aerate the aquaria are pumped 

 in by a wind-mill. 



Mr. Agassiz carries on his own investigations in the smaller 

 room at the west end of the building. The larger room of the 

 ground floor each summer he generously puts at the disposal of a 

 certain number of students from the Museum of Comparative 

 ZoSlogy at Cambridge, Mass. 



Any day through the summer you may see half a dozen men 

 here industriously bending over their microscopes, studying ani- 

 mals in their living form or preserving material for future study. 

 On account of the extreme moisture of the atmosphere, little 

 balsam mounting or clearing can be done at the sea-shore, so that 

 work of this kind is usually postponed to be done at Cambridge 

 during the fall and winter months. 



Each morning at nine o'clock a hack from the boarding-house 

 in town puts the men down at the laboratory door. It calls for 

 them again at Ave, after their day's work is ended. 



About ten o'clock each evening "Thomas," Mr. Agassiz's faith- 

 ful man-of-all-work, rows slowly up and down the cove skimming 

 the surface of the water with a tow-net. Froni time to time he 

 lifts the net of tine cheese-cloth carefully from the water, turns it 

 inside out and dips it repeatedly in a bucket of water. 



The soup thus obtained is carried into the laboratory, diluted, 

 and poured out into half a dozen glass dishes placed on black 

 tiles. 



Around these dishes the men gather upon their arrival in the 

 morning, each furnished with pipettes and watch-glasses of various 

 sizes. Every nook and corner of the dish is carefully scanned 

 with naked eye and with the aid of lens, and in diflferent lights, 

 that no egg or larva, however minute, may escape notice. 



After a man has acquired a general knowledge of the pelagic 



fauna, he usually confines his attentions to some particular group 

 of animals, and the tow is sorted out and divided accordingly. 



One man studies the moUusks, another the echinoderms, an- 

 other the jelly-fishes, and so forth. 



The tow is the chief source of material for study. It is supple- 

 mented, however, by dredging from the steam-launch, and shore 

 collections at low tide. 



The laboratory contains a good library of general works of refer- 

 ence, while literature on special topics is supplied from Mr. 

 Agassiz's private library and from the museum library at Cam- 

 bridge. 



Not least among the advantages afforded to the training inves- 

 tigator are the helpful suggestions of Mr. Agassiz himself, whose 

 long experience in marine work makes him an invaluable ad- 

 viser. 



With such excellent opportunities for advanced work in zoology, 

 it is not surprising that in this little laboratory material has been 

 gathered for many scientific papers of a high order, and that here 

 many of the best zoologists Harvard College has produced have 

 I'eceived an important part of their professional training. 



BACTERIOLOGY IN THE DAIRY. 



BY C. C. GEOBGESON, MANHATTAN, KANSAS. 



The bacteria which affect the quality of our dairy products 

 may, for practical purposes, be classed under two heads, namely, 

 those which are beneficial, and those which are injurious, and it 

 is as essential to encourage the one as it is to wage a constant war 

 upon the other. It has been established beyond a peradventure 

 that the pleasant flavor and aroma of good butter are developed 

 by certain species of bacteria present in the cream and instru- 

 mental in producing the changes which take place during tlje 

 process of fermentation usually termed "souring." And it is 

 equally well established that there are certain other species which, 

 if permitted to get the mastery, will, as it were, overpower and 

 neutralize the influences of the former class and give a disagreea- 

 ble taste and smell to the butter. Both classes are present in all 

 dairies, and the skill and success of the butter-maker depend in 

 large degree on the recognition of this fact and his ability to foster 

 the growth of the beneficial bacteria and to keep the injurious 

 kinds in subjection. His chief weapon against the latter is clean- 

 liness. Filth of every description is their best breeding-ground. 

 But it also happens that the conditions are such, in surrroundings 

 over which the butter-maker has no control, that, in spite of the 

 strictest cleanliness on his part, the injurious organisms propagate 

 toofastand deteriorate his products. Again, itmay lie in the health, 

 feed, or other conditions affecting the cows from which the milk 

 is drawn. Under such conditions, what is he to do? It is the 

 solving of this problem which has brought bacteriology into inti- 

 mate connection with the dairy business ; and the honor of solving 

 it and thereby ensuring the production of "gilt- edge" butter 

 under naturally adverse conditions belongs to the Danes. 



In practical dairying there are two forms of physical means by 

 which the growth of bacteria may be controlled, namely, cold and 

 heat, relatively speaking. At a temperature at or near the freez- 

 ing-point the active growth of the bacteria ceases, and hence the 

 reason for keeping the milk cool by the use of ice. The cold pro- 

 duced by the ice does not kill the organisms or purify the milk, 

 it simply retards their multiplication, and thus affords time for 

 the dairy operations to take place before they work injurious 

 changes. Heat, on the other hand, kills the bacteria. At the 

 boiling-point nearly all those forms ordinarily found in milk are 

 destroyed. But, as this high temperature affects the taste of the 

 milk or cream by imparting the characteristic " boiled taste," in 

 practice the temperature is raised to but 75" or 80° C, at which 

 point the taste is not materially affected, and still the greater 

 portion of the bacteria are killed. 



This much known, the Danes have gone a step farther. They 

 have isolated and perpetuated "pure cultures" of those forms 

 which they have found to be beneficial to the production of first- 

 class butter, and by impregnating the cream, under proper condi- 

 tions, with these artificially grown bacteria they give their butter 

 the desired flavor and aroma. It is now between two and three 



