. Biologisches Zentralblatt. Biology. grown individuals such as those shown in Fig. 3. In the remain- ing animals left in the aquarium the ratio of siphon to body length was unchanged on Mar. 18th., as indeed it remained in later growth ander the same conditions. Moreover, although there was considerable Variation in different individuals, the animals in the food culture showed a much more rapid rate of total growth than those remaining in the aquarium. This is not to be wondered at, since the former could always be seen to have their gut crammed with green algae and other food- stuffs. One in
. Biologisches Zentralblatt. Biology. grown individuals such as those shown in Fig. 3. In the remain- ing animals left in the aquarium the ratio of siphon to body length was unchanged on Mar. 18th., as indeed it remained in later growth ander the same conditions. Moreover, although there was considerable Variation in different individuals, the animals in the food culture showed a much more rapid rate of total growth than those remaining in the aquarium. This is not to be wondered at, since the former could always be seen to have their gut crammed with green algae and other food- stuffs. One individual, for ex- ample, taken from the aquarium on Mar. 5th. measured 1,5 cm extended. On that date it was placed in a jar with weed growths, and on Mar. 18th. it measured 4,5 cm, i. e. its length had in- creased by 3 cm. In contrast to this, the greatest growth of any individual in the aquarium during the period Mar. 5 —18th. was -5—1 cm. After having been photo- graphed on Mar. 18 th., theanimal shown in Fig. 4 was placed back in the aquarium again. Fig. 5 (3/4 nat. size) shown this same individual on Mar. 27 th., i. e. 9 days later. Its absolute size had increased considerably, but the oral siphon was relatively shorter again as comparedwith the rest of the body, tending to resume the ratio characteristic of animals grown throughout in the aquarium. With this should be compared Fig. 6 (3/4 nat. size) which shows one of the animals left in the food jar as it appeared on Mar. 27 th., the date on which Fig. 5 was photographed. The essential points, then, are that removal of aquarium-grown animals to a jar containing an abundant growth of algae produces a great increase of the oral siphon length as compared with the length of the rest of the body. Replacement into the aquarium brings about a relative shortening of the siphon again as further growth proceeds. It should be further mentioned that the same effects were obtained repeatedly. Series II of experiments is alone give
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Keywords: ., bookauthorro, bookcentury1900, bookdecade1910, booksubjectbiology
