8 SIDNEY F. HAEMEB. 



II. The Male Sexual Elements. 



There canj however, be no doubt of the existence of sperma- 

 tozoa in Cyclostomes, although I am not aware that they 

 have previously been described. 



In Crisia I have usually found them in colonies without 

 ovicells^ (17, p. 145), although they occur in ovicell-bearing 

 colonies in Idmonea serpens. 



The spermatoblasts occur in masses filling up a large portion 

 of the body-cavity of sexual individuals. The sperm mother- 

 cells in both Idmonea and Crisia seem to occur in groups 

 of four (PI. I, fig. 4) ; and the four flagella when first 

 developed appear, under insufficient magnification, as if they 

 belonged to one cell. The mature spermatozoon (fig. 4) 

 possesses an elongated head (measuring about •0064 mm.), and 

 a long, active flagellum. 



In C. cornuta it was noticed that a delicate, hyaline layer 

 of endocyst protruded from the aperture of the zooecium, 

 during the escape of the spermatozoa, in the form of a cone at 

 the apex of which the spermatozoa escaped. 



III. The Origin of the Secondary Embryos. 



My observations on this part of the subject have been made 

 almost entirely by means of sections. The ovicells were pre- 

 served and decalcified, at one operation, by placing in a mixture 

 of corrosive sublimate, nitric and acetic acids. The most suc- 

 cessful staining was obtained with Grenacher's hsematoxylin 

 or with borax-carmine, in the latter case washing with alcohol 

 containing picric acid. 



The free larva of C. eburnea is well figured by Barrels 



(1, pi. iii, fig. 23). It is, roughly speaking, cylindrical in 



shape, being covered externally by a complete coating of cilia. 



At one end of the cylinder is an aperture leading into the 



" sucker," by means of which fixation is eflPected ; and, at the 



opposite end, is another aperture leading into the so-called 



' In one case, spermatozoa were found in a colony of C. cornuta, which 

 bore a single very young ovicell. 



