Fuchs, The effect of abundant food on the growth of young Ciona iutestinalis. 433 



and on April II th. a marked shortening of the siphon was again 

 apparent - - see Fig. 9 (3/4 nat. size.) 



This series consequently proves that the siphon elongation in 

 the food cultures is due to the abundant food itself, and not to 

 the other conditions which are different from those prevalent in 

 the aquarium. 



This effect of feeding on the growth of Ciona gains additional 

 interest when the condition of mature individuals in their natural 

 habitat is considered. Animals collected from different localities 

 in the Bay of Naples are found to have the oral siphon of 

 different lengths relative to that of the body. Individuals from 

 any given spot, however, agree more or less among themselves in 

 having the siphon longer or shorter. Some have the ratio of the 

 siphon to the body length similar to the aquarium-grown young 

 animals, others have a proportion intermediate between that of 

 aquarium and food culture specimens. None, however, have the 

 excessively long siphons of the last mentioned. That some localities 

 should offer a richer food supply than others is extremely likely, 

 and the laboratory experiments indicate that the variations in relative 

 siphon lengths found in nature are attributable to this cause. The 

 absence of animals with extremely elongated siphons is not sur- 

 prising, since the food supply in the sea could scarcely ever be as 

 abundant as in the culture jars ot the experiments. 



Description of Figures. 



The photographs were taken of the animals in the fully extended condition 

 under water. Owing to the weakness of the negatives, the actual photographs could 

 not be reproduced. The figures are accurate outline tracings taken from the 

 photographic prints. In each figure the cross line at the base of the oral siphon 

 is the peripharyngeal band. 



Series I. 



Figs. 1 & 2. Photographed Mar. 27, X 3/4. Typical aquarium-grown animals, 

 from eggs fertilized Dec. 14. 



Series II. 



Fig. 3. Photographed Mar. 5, X 9/11. One of a number of animals which came 

 through the circulation and grew in the aquarium. After being photographed 

 these were placed in Jar A, with abundant weed growths. 



Fig. 4. Photographed Mar. 18, X 3 ,'4. Typical animal from Jar A. After being 

 photographed it was replaced in the aquarium. 



Fig. 5. Photographed Mar. 27, X 3/4. Same animal as Fig. 4, after having been 

 back in the aquarium since Mar. 18. 



Fig. 6. Photographed Mar. 27, X 3/4. Typical animal remaining in Jar A. 



Series III. 



Fig. 7. Photographed Mar. 19, X 9/11. Typical example of aquarium -grown animals 

 (about 3 months old) which were placed on Mar. 19: 



I. In jar of aquarium water containing abundant growths of weed. 



