CATALOGUE OF TUNICATA. 65 



which are given off chiefly near the bases of the peduncles (PI. Dist. I., 

 fig. 2), and are found to be encrusted with sand and shell fragments. 

 The Ascidiarium is frequently flattened so as to assume an equilateral- 

 triangular shape as seen from the side (fig. 10). The peduncle is from 

 twice to six or eight times the length of the Ascidiarium. The stolon is 

 of much the same thickness and appearance as the peduncles. The 

 peduncle is of a dull yellow colour, but the Ascidiarium varies consider- 

 ably. It is sometimes of a dark brown colour, with narrow light- 

 coloured streaks between the rows of Ascidiozooids, sometimes yellow 

 or grey or slate colour, and in a few cases it is a dark purple brown. 

 The following measurements are taken from an average-sized specimen : 



Length of peduncle ... ... ... 9'7 cm. 



Diameter of peduncle ... ... 6mm. 



Length of Ascidiarium ... ... 4'4 cm. 



Breadth 3-3 cm. 



Thickness ... ... ... ... 1-8 cm. 



There is a great variation in the size. The peduncle may extend up to 

 22 cm. and the stolon to 10 cm. 



The Ascidiozooids are closely placed and are arranged in double 

 vertical rows, the Ascidiozooids in each pair of rows being placed oppo- 

 site to one another and alternately with those of the next double row 

 (PI. Dist. I., fig. 3). Very little test is left between the Ascidiozooids, 

 and so the test is soft and flexible and not elastic. In the upper part of 

 the peduncle where it joins the body the young Ascidiozooids may be 

 seen developing. At the top of the Ascidiarium, where the rows have 

 diverged somewhat, the old Ascidiozooids are decaying and falling out of 

 the white transparent test, and there is generally a narrow band at this 

 edge free from Ascidiozooids. In the young colonies attached to a 

 stolon (fig. 11) the slender peduncle rises to a considerable height before 

 a terminal knob forms in which Ascidiozooids develop as young buds. 

 In fig. 11 the youngest colony has a peduncle 3 cm. in height and 

 the next 7 cm., and in both of these the Ascidiozooids are still in an 

 embryonic condition. On an average there are about 20 double rows of 

 Ascidiozooids in a colony. The colony shown in fig. 1 differs from all 

 the others in having the body of a dark purple brown colour, which is 

 found to be due to a dark brown pigment thickly disseminated in the 

 mantle of the Ascidiozooids. Each Ascidiozooid is about 2 mm. in 

 length and about 1 mm. in breadth. The thorax and abdomen are about 

 of the same size. Vascular appendages are continued from the posterior 

 end of the abdomen downwards into the stalk. 



