20 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



stricted into a series of segments with, in S. pinnata, and in most other 

 species, one egg in each. This has gone a little further in the chain-salpee 

 shown in Plate XXVI, A, B, C and Z>, and in the reconstructions which 

 are shown in Plate V, Figs. 2, 3 and 4, although the eggs still lie in a 

 straight line in a plane which corresponds with the middle of the stolon. 

 At a stage a little older, Plate XXV, Figs. 5, 6 and 7, F, O and H, and in 

 the reconstruction in Plate VI, Figs. 1, 2, 3 and 4, the single row is broken 

 up into two, and the eggs are carried alternately to the right and to the 

 left, with the growth of the bodies of the salpa3, until they finally assume 

 the positions shown in Plate XXXVIII, Figs. 95 and 99, n, and Plate 

 VII, Fig. 4, n. The path which is taken by the egg in its migration, 

 and its relations, and that of the testes, to the other organs of the body, 

 will be fully described in the chapter on the process of budding. All that 

 concerns us here is the attachment of the egg to the wall of the cloaca by 

 means of the fertilizing duct, Plate XXXIX, Fig. 4, x, which ultimately 

 becomes a tube, Plate X, Fig. 10, x, and Fig. 1, x, through which the 

 spermatozoa reach the eggs. Most writers state that the egg is fastened 

 to the wall of the pharynx, and it is difficult to decide, from the exam- 

 ination of adults alone, whether the point of attachment lies in the 

 pharynx or in the cloaca, for there is nothing to mark the boundary 

 between these structures, which are, however, more sharply separated in 

 the young chain-salpa, where the duct is clearly seen to be attached 

 to the wall of the cloaca. 



The chain-salpae of S. pinnata are set free in wheel-shaped or cylin- 

 drical clusters of eight or nine individuals each, Plate I, Fig. 2. At 

 the time of birth each of them contains an unfertilized egg, essentially 

 like the one from Salpa hexagona which is shown in Plate X, Fig. 1. 

 The large nucleus with its network of chromatin threads and large 

 nucleoms is surrounded by a granular yolk, which is enclosed by a 

 capsule of follicle cells, which are now elongated, although they were so 

 flat as to be scarcely visible at the stage shown in Plate XXXVI, Fig. 2. 

 At one point the follicle is continuous with the fertilizing duct, x, which 

 has, by most writers, been termed the oviduct, although there is no good 

 ground for the use of this name, for no ova ever pass through it ; and while 

 it may possibly be homologous with the true oviduct of other tunicates, 

 there is no evidence that this is the case, and I therefore prefer to use a 

 name which at least has the merit of expressing its function, at the 

 present day, as a channel for the spermatozoon. 



