75 



the tissues at early periods, obviating to some extent the 

 necessity of the more difficult anatomical investigations. 



In the newly completed organism of the Nephelis the 

 character and course of the circulation can be distinctly 

 traced, the wave-like contractions of the vessels being 

 indicated by their colored blood ; in the lateral vessels 

 proceeding from behind forward on one side and down- 

 ward on the oj^posite. I have not been able to discover 

 the irregular movements described by some writers, now 

 advancing and again retreating in the same vessel, at 

 different times. 



In the embryo of the Clepsine sex-puncto-lineata the 

 histogenic transformation distinctly occurs at first in the 

 superficial strata of cells, which as they change become 

 translucent, while the interior is still composed of the 

 minute yellow cells of the original yolk. At an early 

 period also the number of segments of the body is but 

 twenty-one or twenty-two, corresponding with the num- 

 ber of pairs of ganglia that at a little later period can be 

 rendered visible by moderate compression. The earliest 

 traces of the lateral coeca of the stomach appear when the 

 yolk substance is reduced to an elongated central mass, 

 as short yellow tubercles produced apparently by the 

 constriction of the rudimentary stomach ; they then elon- 

 gate and gradually acquire the branching character of 

 maturity. The embryo is born before the completion of 

 the alimentary canal and without an oral orifice, but the 

 posterior sucker is already fully developed for attachment 

 to the body of the parent. It remains in that position 

 until, through a more complete development, it becomes 

 capable of an independent existence. In short the entire 

 process of development which has been minutely traced 

 by Grube, Weber, v. Rathke, Leuckart and others admits 

 of more facile examination than the embryology of the 



