98 TUNICATA—SALPIANS CHAP. 
further division, to the sexual generation, which is polymorphic 
having three distinct forms, in two of which the repro- 
ductive organs remain undeveloped. 
The primary buds are constricted off while still very young 
and undeveloped (Fig. 60, D, B, and E); they migrate from their 
place of origin on the stolon, over the surface (aided by large 
amoeboid test-cells which become attached to the buds) (Fig. 60, 
B), multiply by fission, and become attached (again by the help 
of amoeboid test-cells and ectoderm cells which form a slight 
= 
Ne 
Fia. 60.—Life-history of Doliolwm. A, tailed larval stage; B, “nurse” or oozooid, 
showing buds (blastozooids) migrating from the ventral stolon to the dorsal process ; 
C, posterior part of much later oozooid to show buds arranged in three rows on 
dorsal process ; D, stolon segmenting; E, young migrating bud; F, trophozooid 
developed from one of the buds of a lateral row. A¢, Atrial aperture ; 6, buds ; Br, 
branchial aperture ; c/, cloaca ; d.p, dorsal process ; end, endostyle ; ht, heart ; 7.0, 
lateral buds; m.d, median buds; n.g, nerve-ganglion ; of, otocyst; p.c, peri- 
cardium ; sk, stalk; sto, stolon. (After Uljanin and Barrois.) 
“placenta”) in three rows—a median and two _ lateral—to 
the dorsal outgrowth (Fig. 60, C) of the body of the nurse. 
This parent-form by this time has become greatly modified, 
and its structure is largely sacrificed for the good of the buds or 
growing zooids, for which it really forms a locomotory organ. 
Its muscle-bands become greatly developed in width (Fig. 60, 
C), and the branchial meshwork, endostyle, and alimentary canal 
disappear. 
The three forms produced in the second generation are as 
follows :—(1) Nutritive forms (“ trophozooids ”) derived from the 
lateral rows of buds, which remain permanently attached to the 
