CATALOGUE OP TUNICATA. 67 



and the arrangement of the alimentary canal. Five of these small colonies 

 are attached to the carapace of a crab, Macippe spinosa, Stimpson. 



Colella claviformis, Herdm.,* PL Dist. III., figs. 1 15. 



External appearance. Thu colony consists of a short, stout peduncle 

 bearing a large irregularly pyriform or ovate body which tapers roughly 

 to a blunted upper extremity. The wider ends of both body and peduncle 

 are at the point where they join (PI. Dist. III., fig. 3). The body and 

 peduncle are of much the same length, and a number of colonies are 

 united together by a mass of branching and anastomosing rootlets which 

 spring from the lower ends of the peduncles (fig. 1). The surface is 

 smooth. The colour is whitish grey, and glistening on the body, and is 

 of a dull yellowish grey tint on the peduncle. The yellowish brown 

 Ascidiozooids show through the grey test, and the abdominal parts of 

 the lowest row can be seen extending into the upper end of the peduncle. 

 The surface of the body is pitted owing to the contraction of the 

 Ascidiozooids, and so each aperture appears to be placed at the bottom 

 of a pit. The peduncle is marked by slight transverse creases and 

 ridges. The dimensions of an average colony are as follows : Length 

 of peduncle 4'4 cm., thickness of peduncle below body l - 5 cm., and 

 at base 7 mm. Length of body 4 cm., breadth of body 3 cm., thickness 

 of body 1'8 cm. 



The Ascidiozooids consist of a small thorax, and an oval abdomen 

 provided with a long vascular appendage, but differ greatly in shape 

 at the upper and lower ends of the colony. Those near the top 

 have short and wide bodies (3 mm. long and 2 mm. broad), and have 

 each an incubatory pouch containing developing embryos, and no 

 reproductive organs in the short intestinal loop ; while those at the 

 base have very long, narrow bodies (5 mm. long and 1 mm. broad) with 

 long U-shaped intestinal loops, no incubatory pouches and masses of 

 reproductive organs placed in the intestinal loops. It is evident that 

 these two sets of Ascidiozooids are at different stages in their life history, 

 and that as the reproductive elements are set free and become trans- 

 formed into embryos, developing in the incubatory pouch, the abdomen 

 shortens considerably in length. 



The test is firm on the outer surface, but soft and whitish-grey, 

 glistening and semi-transparent in the inside of the upper part of the 

 colony ; while in the peduncle it is tougher and more opaque, and of 

 a yellower tint. On section the test is very smooth and dense like 



* See "Re vision, "p. 611. 



