ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 773 



Though fairly successful, several difficulties arose, but these were sur- 

 mounted. The chief object was to obtain simultaneous hauls at various 

 depths, and it was found difficult to prevent the long wire-rope from 

 twisting. The difficulty was solved by an arrangement by which a 

 shackle, to which the appliance is fastened, moves freely round the 

 wire. By this means it became possible to have no fewer than ten 

 appliances out simultaneously from two wires. 



The material obtained was very large, and quite a number of pelagic 

 deep-sea fish not previously described was discovered. A large trawl 

 was also used ; this made twenty hauls. The results were successful, 

 but do not appear to include any new discoveries. 



Studying the Relation between Light and Pigment Formation 

 in Crenilahras and Hippolyte.* — The vessels used by F. W. Gamble 

 consisted of large bell-jars, supplied with an air or water current, or 

 stirred by a glass plunger. Seasoned vessels, as well as sterilized ones, 

 were used ; filtered " outside " and tank-water were respectively em- 

 ployed ; diatoms and algas were used as food. The vessels were shaded, 

 exposed to diffuse light, and kept in darkness ; the backgrounds were 

 translucent, absorbing and reflecting ; the incident light used was 

 monochromatic (red and green) as well as white light. The temperature 

 was kept down to 16° C. by a water-jacket, and in other cases allowed 

 to rise to 18° C. or over, but in spite of ail these variations the larvse 

 survived only about ten days. The monochromatic screens used in the 

 case of larvae consisted of selected pieces of coloured glass (ruby or 

 green) combined with coloured gelatin films. These were placed over 

 the inverted belljars, the sides of which were converted into absorbing 

 or reflecting backgrounds. A continuous air-current was led into the 

 water, and the covered screen was cut so that its halves embraced the 

 air tube, which was blackened at this point. The junctions of the 

 screen with the bell-jars consisted of black velveteen, so as to cut out 

 any oblique white rays, but it was found that great care is needed to 

 avoid liquefaction of the gelatin films. In order to observe the pro- 

 longed effect of monochromatic light, and to obviate the dominant 

 influence of the background, fluid screens were constructed. To insure 

 a fairly strong light, the screen was made of one cell only. A double 

 glass vessel, consisting of two beakers, or of two large cuvettes, the 

 inner one standing on glass supports, so that its rim just cleared that 

 of the outer vessel, was employed. The inner vessel was then provided 

 with young transparent Hippolyte in filtered water, and finely divided 

 Ceramium was used as food. The space between the two was then filled 

 with the colour filter, until the level exceeded that of the water in the 

 inner vessel, the top inch or so of which was rendered opaque. A cover 

 of glass, or of glass and gelatin, was placed over the double vessel, and 

 the whole was then transferred to a shallow aquarium in a strong light. 

 In one case a circulation of tank water was maintained in the inner 

 vessel. The main point of the apparatus is to provide a means of 

 flooding the animals with transmitted coloured light, and thus largely to 

 avoid the effect of light reflected from an absorbent or deflecting back- 



■" 



* Qunrt. Journ. Micr. Sci., lv. (1910) pp. 553-5. 



