Clurtoptcrus Variopedatus. 511 



short protuberance which is commonly referred to as the "terminal 

 papilla." 



FuRTiiEK Growth of the You^s^g Tkochophore. 



When the young trochophore is about sixty-four hours old it is 

 somewhat spindle-shaped. Its first mesotrochal band of cilia has 

 begun to be atrophied and there remains to represent it only the 

 pair of strong lateral flagella which may be seen vibrating rapidly. 

 At the same time that the first ciliated band is undergoing atrophy 

 a second circle is suggested by a gradual lengthening of the cilia 

 around the region of the body within which is the intestine. Its 

 alimentary canal practically fills all of the body cavity. The mouth 

 has enlarged transversely and its anterior (upper) lip has the form 

 of a lobe. It leads by a spacious ciliated osophagiis into the spherical 

 stomach which occupies the middle region of the body. The intes- 

 tine is a short conical cavity separated from the stomach by a con- 

 striction or double fold of the entoderm layer. The intestine does 

 not quite fill the perivisceral cavity posteriorly. Dorsally it opens 

 to the exterior by the anus which is just in front of a "terminal 

 papilla" that bears a tuft of long non-vibratile cilia. Many of the 

 young trochophores have small pellets of diatoms in the stomach 

 at this age. 



The larvae of six days are much like those described, and while 

 they may be kept alive twelve or fourteen days in the aquaria do 

 not seem to thrive. This is due to a lack of proper food in the 

 aquaria, as I would judge from one culture of larvae that was larger, 

 at five and one-twelfth days, than any lan^se reared during the two 

 previous summers. At this age they had the characters by which it 

 was possible to connect the older larvie which I reared in the 

 aquaria, with those taken in the tow. 



The form of the larva six days old (Text-figures A and B) is 

 either somewhat spindle-shaped or cylindrical according as the body 

 may be changed by muscular activity. It is somewhat longer and 

 more transparent than in the younger specimens. It is covered with 

 cilia which are everywhere of unifonn length, excepting in the 

 ciliated girdle around the posterior region of the larva, a pair of 



