274 FRESH-WATER AQXJAEIA. 



diminished, imtil only one or two of them have been left. 

 One sex is not more guilty than the other of this un- 

 natural practice. 



Vallisneria spiralis is about the most suitable plant to 

 place in an aquarium which is to contain these Spiders. If 

 possible, there should be no other animals associated with the 

 Argyronetse, except those which are intended for their food. 

 A large snail is very likely to disturb the subaqueous nests and 

 set free the air which they contain ; while a fish would be 

 greatly tempted to devour a spider. If the small tank which 

 is set apart for the Argyronetse is properly situated in regard 

 to light, little or no confervae will interfere with the clearness 

 of either the glass or the water ; and the interesting habits 

 of these animals cannot, of course, be satisfactorily watched 

 unless both the glass and the water are perfectly transparent. 

 This transparency is easily maintained. For example, the 

 water of the aquarium in which I had some Spiders was not 

 changed for nearly, if not quite, a year, and it seemed to be 

 just as clear then as it was upon the day I first introduced 

 it. This aquai'ium was covered with glass in such a way that 

 air could be freely admitted, and it was placed about 6ft. 

 from a window which faced due east. In this position the 

 light was quite good enough to allow all the movements of 

 the Spiders to be seen, and not sufficiently strong to cause 

 the growth of the sight-impeding conlervse. Other aquaria 

 were in the same position, and all were as perfectly clear as 

 this one, and gave little or no trouble. These circumstances 

 are mentioned here in order that novices in aquarium matters 

 may not think that it requu-es any skill to preserve the 

 water of small portable tanks in a perfectly clear and bright 

 condition. A little care is the only thing necessary to attain 

 this end. 



Argyronetse often remain above the surface of the water, 

 especially when first placed in an aquarium. However, 

 after a day or two, if they are healthy, they wiU enter the 

 water and begin to construct their nests. The vessels in 

 which these animals are confined should be covered, or they 

 wiU escape.- When flies are not taken by the Spiders after 



