244 



THE RELATIONS OF PROTOZOA 



w- 



119, 120), it turns out that nothing but a certain general, exter- 

 nal resemblance in form is the basis upon which their relation- 

 ship has been claimed.* 



Protozoa and Articulata. The fallacy of certain alleged tran- 



whii'h it hc'on". V>o.-om pvident at an early period. This may be as well 



illustrated by its growth in the bud as by 

 that in the egg. The bud commences as 

 & a mere internal, globular projection, (fig. 

 ca 120, bd, and fig. 140c, a,) formed by 

 the two walls (fig. 140c, w, w 1 ) of the 

 general cavity. The first indication of 

 a cavity appears in the form of a hol- 

 wl lowing (ca) in the core of the bud. In 

 process of time the bud elongates and 

 doubles upon itself, (fig. 140c, t to s/ 1 ,) 

 and, one end becoming broadened, a cir- 

 cle of feelers, (/,) fourteen in number in 

 Fredericella, becomes apparent, at first as 

 a scalloped edge, whilst the internal wall 

 t is differentiated into a general muscular 

 layer (H> 2 , w 3 ) and a group of distinct mus- 

 cles (r, r 1 , r 2 ,) like those of the adult. 

 "When the organs have developed to a 

 certain degree, the walls of the stem opposite the two ends (at t and an) of the 

 body of the embryo are perforated by a process of resorption, and the young 

 Bryozoan is at liberty to protrude its head, and commence its first meal. 



* In all probability Van der Hoeven was led to suggest the relationship of 

 Vorticellte to Bryozoa by the assertion of Ehrenberg that the former possesses a 

 distinct intestine which doubles upon itself, somewhat in the way that it does in 

 the latter. Subsequent naturalists, being led to disbelieve the truth of Ehren- 

 berg's observations, have had far less reason than the Hollandish observer to 

 claim such a position for the Vorticellae. 



Fig. 140c. The end of a branch of Fredericella regina, Leidy, MS., with 

 two young budding. 100 diam. ek, the parchmenty sheath; w, the outer, and 

 w 1 , w 2 , te3, the inner walls, the latter having a semi-muscular nature ; a, 6, the 

 two walls of the incipient bud; ca, the first trace of a digestive cavity; /, the 

 incipient tentacles of a far-advanced bud ; s/ 1 , the stomach ; an, the posterior end 

 of the intestine ; r, r 1 , the right and left retractor muscles of the head ; r 2 , the 

 retractor muscle of the intestine, projecting over st l like an outer wall at r 3 , and 

 forming a continuous layer over the head (at H) in connection with w 2 . 

 Original. 



w tk 

 Fig. 140c. 





