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



these bowls were then immersed in an aquarium tank, through 

 which a continual stream of water was flowing. Here they under- 

 went their early growth and development, all exposed to more or 

 less the same conditions of light, temperature and food supply. 



In such aquarium tanks at Naples, besides the cultures in- 

 troduced, young individuals of Ciona appear sporadically on the 

 walls. These must come in as larvae through the sea water cir- 

 culation, and their apperaance is unavoidable unless the incoming- 

 water be specially filtered. The latter precaution was, of course, 

 taken when different pure families were being raised, but in the 

 preliminary investigations of which the following are a part it was 

 unnecessary. The growth of some such accidentally introduced 

 individuals is discussed below. 



Figs. 1 and 2, forming Series I, are from photographs (3/4 natural 

 size) of typical living individuals, nearly 3 ! / 2 months old, from an 

 aquarium culture. The only important point to notice in them for 

 our present purpose is the relative length of the oral siphon to 

 that of the rest of the body. 



In Series II *), illustrated by Figs. 3 6, some of the animals 

 growing in the aquarium were removed to water containing a much 

 more abundant food supply, and the growth of these was compared 

 with that of the remainder of the animals, still in the aquarium. 

 Fig. 3 (y/11 nat. size) shows a typical animal from the aquarium. 

 It was taken on Mar. 5, and like all the other photographs, exhibits 

 the living animal in the expanded condition under water. The 

 feature to observe in Fig. 3 is the relative shortness of the oral 

 siphon as compared with the length of the remainder of the body. 

 The ratio between the two was more or less constant in all the 

 aquarium-grown animals. 



The aquarium contained only a meagre growth of algae on its 

 walls, and the transparent tissues of the young animals showed 

 that, although the gut always contained some food, it was never 

 full. On Mar. 5th., immediately after the photograph had been 

 taken, some of the animals were removed from the aquarium into 

 a jar of about 2 litres capacity, the walls of which were covered 

 by a thick and abundant growth of green algae. The other individ- 

 uals were left in the aquarium. 



On Mar. 18th., that is 13 days after the transfer, the animals 

 in the jar of food culture were found to have completely altered 

 in appearance. The oral siphon had become relatively 

 enormously long. Fig. 4 (3/4 nat. size) is a typical individual 

 from the food jar. The oral siphon approaches in length that of 

 the rest of the body, and is an extreme contrast to the aquarium- 



]) All the individuals of Series II were ones which had come through with 

 the circulation water & settled and grown on the walls of the tank. 



