68 



YVES B. PLESSIS 



conditions the gaseous exchanges between 

 the air and water attain their maximum 

 activity. Most of the algae spread out 

 and assume strange forms; C odium to- 

 mentosum. for example, develops a thick 

 knobby cover. This technique for culti- 



Figure 13. — General plan of equipment for culti- 

 vation of algae : A, inlet of water ; B, outlet 

 of v/ater. The general plan without the top 

 plate is shown at top ; a cross section showing 

 the top plate is at the bottom. 



vation of algae raised on glass, commer- 

 cially known in France by the name of 

 "lessive,'' permits the complete isolation 

 of volumes of air which are important for 

 raising aerobic marine invertebrates sep- 

 arately upon a blanket of Godium sp. 



-*[=? 



//// 1^/// > / ' // /// /////////.'/////.'//////,■ 



'//////' ^// 



Figure 14. — Cut-away section of algae-cultiva- 

 tion equipment : A, inlet of water ; B, outlet of 

 water. 



•,w • '//■'/ 



Figure 15. — Cut-away section of a plate of the 

 "lessive" type: A. inlet of water; B, outlet 

 of water ; C, glass rod for breaking up the flow 

 of water ; D, bar of glass fastened to the top 

 plate for breaking up the flow of water. 



CONCLUSION 



We have acquired our experience in 

 "aquariology"' by looking for special solu- 

 tions to problems of experimental ecology. 

 The rules that we have worked out gradu- 

 ally will perhaps enable others to save a 

 good deal of guesswork. The actual 

 establishment of special habitats is even 

 now most helpful in the field of experi- 

 mental investigations. 



The needs of the public aquarium are 

 different from those of a research aquari- 

 um where the care for the living condi- 



tions of the occupants is not combined 

 with esthetic preoccupations. Many of 

 the techniques described here have been 

 conceived for the purposes of experi- 

 mental ecology and cannot be transposed 

 directly ; on the other hand, the aquarium 

 with a sand bottom — presented in a tank 

 with nonparallel sides and with inclined 

 glass — is certainly a fortunate transposi- 

 tion from the experimental scale to the 

 large-scale public presentation. 



