Fuchs, The effect of abundant food on the growth of young Ciona intestinalis. 431 



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 under 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 ajar 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. 18th., the animal 

 shown in Fig. 4 was placed back 

 in the aquarium again. Fig. 5 

 (3/4 nat. size) shown this same 

 individual on Mar. 27th., i. e. 9 

 days later. Its absolute size had 

 increased considerably, but the 

 oral siphon was relatively 

 shorter again as compared with 

 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. 27th., 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 

 given in detail here, as an illustration of the general result. 



28* 



8 



