8o RITTER. [Vol. II. 



longer homogeneous and clear, but is filled with granular sub- 

 stance. In some of these last-described ova the nucleus still 

 maintains the large, clear, spherical, vesicular character which 

 it presents throughout the amoeboid period. In others, how- 

 ever, it is indistinguishable. This last condition probably indi- 

 cates the period of maturation. 



In addition to these several stages of development of the 

 ovarian ova, numerous stages, from the two-celled stage on- 

 ward, in the development of the embryos have been found. 



Finally there occur numerous packages of tadpoles, each 

 package containing from ten to sixteen or more individuals, 

 situated in cavities of the semi-cartilaginous test of the colo- 

 nies. These cavities are almost perfectly spherical, are remote 

 from the surface of the colonies, and are entirely closed. They 

 contain nothing but the closely packed tadpoles ; and after 

 these have been picked out the firm, smooth walls of the 

 cavities remind one of bullet molds. 



The tadpoles themselves are enveloped by an unusually 

 thick layer of what in all probability corresponds to the test 

 formed at an early time in the embryonal life of all ascidians. 

 But it contains an unusual number of cells, and in addition 

 bodies of various kinds, which I can account for in no other 

 way than by supposing them to be remnants of the parental 

 zooids which produced the ova. 



In fact, there is little room for doubt about the nature of 

 some of them. Thus, in one instance in particular, a small 

 cluster of them resembled the large yolk containing mesen- 

 chyme bodies of the adult zooids so strikingly that I should 

 not have thought of questioning their nature but for the 

 remarkable position in which they occurred. 



Besides these bodies, pieces of fibers are found which are 

 almost certainly remnants of the muscle fibers of the paternal 

 mantle. 



In some instances the tadpoles are in an advanced stage of 

 metamorphosis while still contained in the cavities. 



Mature spermatozoa, as well as others in various stages of 

 development, are abundant in most, if not in all, of the post- 

 abdomens. 



