186 THE AMERICAN NATURALIST [Vol. XLV 



the Planorbis was not breeding, transferred some Ana- 

 charis and a number of mature ancyloids to a new 

 15 X 9-inch jar, taking care not to introduce any Plan- 

 orbis. May 3, 1909, the first ancyloid hatched in the jar 

 was noticed; it was about half the size of the parents. 

 Others appeared later. By December, 1909, the parent 

 stock had disappeared and the stock hatched in the jar 

 remains very small, indicating some unfavorable condi- 

 tion. The bottom of the jar was covered with a mixture 

 of ordinary and swamp soil, but the supply of swamp 

 soil used in previous jars having been used up, that in 

 the present jar was taken from another place, and may 

 have contained some unfavorable matter. The Ana- 

 charis in the jar is fairly flourishing, but there is no 

 green algal growth. 



General Conclusions. — The Gundlachia may repro- 

 duce before assuming the completely mature form. The 

 shell varies in apparent color in accordance with the 

 muddy or sandy character of the bottom soil, but the 

 dark coating in the former case is not incorporated with 

 the shell structure. 



The ancyloid stage has a period of least activity in 

 May. In July and August the septates appear. In au- 

 tumn and early winter the third stage is developed, be- 

 coming mature and complete in February or March. 

 This course is, however, not invariable in the aquarium 

 or domesticated specimens, since Mr. Allen has taken 

 ancyloids in January or February, an irregularity prob- 

 ably due to temperature and which might not have oc- 

 cured in specimens under perfectly natural conditions. 

 It is not certain that the ancyloids detected by Mr. Allen 

 in July and August were the young of that season, since 

 the minute creatures are very difficult to detect in the 

 aquarium and can not be handled. They are so trans- 

 lucent in the younger stages as to be practically invisible. 

 However, it is probable that the eggs are laid during the 

 winter and hatched in the very early spring. 



It seems likely that under average conditions only a 



