78 CRISTATELLA MUCEDO. 



Professor AUman states that the colony is strictly annual. These 

 are enquiries which open up large fields of research in one of the 

 most beautiful and attractive branches of microscopic study. 

 Here alone is summer and autumn occupation for ardent micro- 

 scopists. The snowy crests of the Cristatella, their sweeping 

 tentacles, and vibrating cilia, will charm the eye of student or 

 non-student alike for many an hour. Its beauty of form only will 

 captivate the latter, but to the former belongs the additional plea- 

 sure of histological research and of tracing its wonderful Hfe- 

 history. 



" Here, to charm the curious eye, 

 A host of hidden treasures lie ! 

 A microscopic world that tells 

 That not alone in trees and flowers 

 The spirit bright of beauty dwells ; 

 That not alone in lofty bowers 

 The mighty hand of God is seen ; 

 But, more triumphant still, in things men 

 count as mean." 



EXPLANATION OF PLATES VIII., IX., X. 



Plate VIIL 



Fig. 1. — Paludicella Ehrenbergi. 



,, 2. — Alcyonella fimgosa. a, ovary; b, testis; c, funiculus; d, 

 spermatozoa. 



,, 3 — 4. Plan of Polyzon, exserted in Fig. 3, retracted in 

 Fig. 4. a, moutli and tentacles ; b, alimentary canal ; c, anus ; 

 d, nervous ganglion ; e, membranous sac ; /, testis ; /', ovary ; g, 

 retractor muscle. 



,, 5. — Plan of Ascidian Tunicate, a, external tunic ; b, middle 

 tunic ; c, internal tunic ; e, respiratory orifice ; g, transverse 

 respiratory bars ; /i, longitudinal respiratory bars; n, mouth; 

 0, oesophagus ; p, stomach ; g, intestine ; r, anus ; t, tentacula ; 

 u, ganglion ; v, heart. 



Plate IX. 



Fig. 1. — Young Cristatella, just hatched. 

 ,, 2. — Subsequent growth of same. 



