[19] FISH CULTURE IN CENTRAL EUROPE. 557 



the climate makes it necessary (as at Berneuchen, Liibbinchen, See- 

 wiese, &c), stoves are employed.* 



The hatching-chambers at Hiiningen, Selzenhof, Eadolfszell, Wilthen, 

 Liibbinchen, Michaelsteiu, Yelp, Zurich, and Neuhausen are of masonry. 



The rooms where the hatching apparatus is kept should be sufficiently 

 lighted by windows placed in suitable position, so as to facilitate the 

 inspection of the eggs and the separation of the spoiled eggs from the 

 good, &c. It is also asserted that a violet or blue light is most favor- 

 able to the embryonal development of the eggs and fish. I accordingly 

 expected to see colored glass employed in some establishments, but my 

 expectations were disappointed. 



I confess that, with Professor Yerson, among others, I am somewhat 

 skeptical as regards the influence of monochromatic (violet) light to 

 the exclusion of the white (composed of various rays of the luminous 

 spectrum) on animal organisms, since, as Yerson thinks, the same num- 

 ber of rays of a given color on which it is intended to experiment, to 

 the exclusion of others, pass through a colorless glass. 



But, to return to the subject to which I referred, it is easy to guess 

 the reason for the absence of colored glass from the hatching-houses, 

 because according to the advanced opinion of our time the eggs will 

 develop better in complete darkness.t Moreover, it is of little impor- 

 tance in industrial establishments whether some think favorably of violet 

 and blue rays, while others have their doubts on the subject, as experi- 

 ments in this matter would seem more appropriate in a zoological lab- 

 oratory. Complete darkness has also its dangers, as it favors the de- 

 velopment of mold, while light favors the generation of green algae. 



Even a simple pavement of beaten clay (at Dachsen) may suffice for 

 a hatching room, and it is certainly preferable to some other pavement 

 made of or covered with cement (Selzenhof, Hiiningen, Berneuchen, 

 &c.) 5 and in this connection I cannot speak too highly of the Berneuchen 

 establishment for the ingenious way of preventing a light and continu- 

 ous movement which, if not hurtful to fish-culture, may injure the build- 

 ing and interfere with the work of the operator. 



As regards the filtration of the water it may be stated that the filter 

 may either be placed in a room immediately adjoining the hatching 

 room or in that room. The selection of a place for the filter will depend 

 on topographical circumstances and on the desire to avoid any unnec- 

 essary enlargement of the building. It is certain, however, that if the 

 filter is placed in the hatching room itself or in one immediately adjoin 

 ing it, this will be found more convenient, as it affords a better chance 

 to watch this useful apparatus without having regard to the state of 

 the weather. 



* Although there are large stoves at Hiiningen, they were not used this year, not 

 even during a period of intense cold, when the temperature of the spring water be- 

 came considerably lower. 



t For this reason, as well as to protect the young fish against their enemies, the 

 hatching apparatus is kept covered. 



