16 S. F. CLARKE. 



the abrancliiate conclition, the dorsal aiifl lateral surfaces of the 

 animal are of a greenish-yellow hue appearing lighter or darker 

 according to the amount of black pigment existing in the different 

 specimens. In this respect there is considerable variation, though 

 none of the specimens are very dark. In most of them yellow is 

 more dominant than the green. Tiie under surface up to and 

 during the time when the branchije arc resorhed is wliite with per- 

 haps a slight tinge of yellow. In giving the course of develop- 

 ment nothing has been said of the time when the embryo escapes 

 from the egg; this was done because the time varies so vciy much. 

 It occurs about the period that the balancers have reached their 

 greatest size ; sometimes however when tiiey are only half-devel- 

 oped and again not until after they have begun to grow smaller. 



The rate of development seems to be dependent upon a number 

 of conditions. Some of the bunches of eggs are much larger than 

 others, and while all those eggs in a small bunch of ten or fifteen 

 will develop with very nearly equal rapidity, of the various indi- 

 viduals in a bunch of one hundred and fifty or two hundred some 

 may progress twice as fast as others. Those upon the outside of 

 the large bunches advance most rapidly and those neai'est the 

 centre the slowest. Temperature also lias a marked effect; if the 

 water is too cold it retards them, if too warm it kills them. The 

 purity of the water too has an important influence; some which 

 were snj)plied with running water growing and developing much 

 more rapidly than others which were in jars where the water was 

 changed but once or twice a day. While in the egg there is but 

 little trouble in keeping them in good condition, but after they 

 have escaped from the eggshells and have absorbed ail the yolk- 

 nourishment, I found great trouble in getting them food. I sup- 

 plied them with various things but did not succeed in pleasing them. 

 Three or four which were placed in an old aquarium where there 

 were a number of snails and a good supply of Protozoa and vege- 

 table growth, grew quite rapidly and did well, while those in my 

 other aquaria developed cannibalistic tendencies, which were shown 

 by their biting each others gills off and the tips of the tails also. 

 A few only escaped mutilation in this way and these few increased 

 in size much more rapidly than their less fortunate brethren. This 

 rapidity of growth appeared to be of great benefit to them, for as 

 soon as their mouths had attained the requisite size they turned 

 upon the smaller members of their family and swallowed them 



