236 JOHNS HOPKINS UNIVERSITY MORPHOLOGIC A.L MONOGRAPHS. 



is filled by the egg, although a small part of it runs past the egg as a 

 tubular opening, X, to the next egg. After each egg is fertilized this 

 tubular portion of the duct gradually becomes constricted off from the 

 part which surrounds the egg, and this is thus completely shut in to a 

 closed capsule or follicle. The cavity of the duct then gradually disap- 

 pears, as is shown in Plate IX. 



There is a conflict of opinion regarding the structure of the duct 

 before fertilization. Barrois figures it (4) in Salpa africana, before 

 fertilization, as a continuous tube with a lumen which runs from 

 the external aperture to the egg. In living specimens of Salpa demo- 

 cratica at the same stage I have found a continuous passage, and have 

 traced the spermatozoa through it up to the egg before the shortening 

 begins. In his first paper (2, p. 183) Salensky figures a lumen in Salpa 

 democratica, Fig. 4, and says : " In the preserved and colored specimens 

 the lumen of the oviduct is not always to be discovered, but in living 

 animals it is found with ease." 



Todarro says that there is a continuous lumen in Salpa pinnata, and 

 in my sections of Salpa hexagona it is clearly shown, as in Plate X, 

 Fig. 10. 



Figure 9 of the plate shows the way in which, after fertilization, its 

 lumen gradually disappears until at last its cells become arranged in a 

 single row. 



These various observations on both living animals and sections of 

 several species show that the act of fertilization initiates the closure and 

 shortening of the duct ; but in his second paper (5), Salensky says that 

 in Salpa pinnata, p. 96 and p. 105 ; in Salpa africana, p. 147 ; in Salpa 

 punctata, p. 327, and in the genus in general, p. 147, it is divided into a 

 solid portion or egg-stalk, nearest the egg, and a distal perforated portion 

 or oviduct with a lumen which runs only about half way from the 

 external aperture to the egg, so that there is no open way for the 

 spermatozoa to reach the egg. The shortening of the stalk begins, 

 according to him, before fertilization, and takes place in such a way that 

 the cells of the imperf orated portion or egg-stalk become merged in the 

 follicle until the egg is thus drawn along to the perforated portion to 

 meet the spermatozoon. 



That these changes take place as he describes them there is no 

 doubt; but my observations show that they occur after fertilization, in 

 Salpa hexagona at least, and that there is at first no solid section in the 

 duct. 



