222 DEVELOPMENT AND HEREDITY. 



remarkable about the development of the colony lies 

 in the fact that the eggs develop in .the tissue of the 

 stolon before the stolon segments itself to form the 

 individuals. 



For explanation of this method of growth, we 

 naturally turn to the ancestral forms of the Tuni- 

 cates. We find among single Ascidians growing 

 fast to rocks, etc., some forms which mature and 

 reproduce sexually, and at the same time produce 

 by simple budding one, or perhaps three or four 

 individuals, which remain fastened to the first near 

 its base. All of these individuals are essentially 

 alike. A grade higher in the scale, we find the 

 group of Botryllus, also stationary, where the 

 young one developed from the egg does not mature, 

 but buds into four individuals, and is said to dis- 

 appear by absorption into the four. These in turn, 

 before maturing, give off other buds, all of which 

 together form a colony. In these later buds, long 

 before development is complete, the egg-cells ap- 

 pear well differentiated, showing that in this respect 

 Salpa is not unique. This early development of 

 eggs, and the rapid reproduction by budding are 

 probably both the result of a great abundance 

 of food. In another stationary group, Perophera, 

 we find a manner of growth more nearly according 

 with that of Salpa. From the egg of Perophera 



