512 Howard Edwin Eiiders. 



lateral flagella that really consist of several parallel flagella, and 

 an anterior flagellum. The mouth is a conspicuous large, ciliated, 

 triangular opening surrounded by thick lips. The pre-oral lobe, or 

 upper lip, is larger than in the younger larvae. It has the form of 

 an overarching hood. The post-oral lobe resembles an inverted hare- 

 lip. From the narrow posterior end of its V-shaped cleft a groove 

 ■which is provided with strong cilia, that beat towards the mouth, 

 extends backward toward the level of the pair of lateral flagella. The 

 brownish red "eyes" or "eye-spots" are larger and more prominent. 

 The gullet is thick-walled and covered with close-set cilia. It passes 

 obliquely backward and joins the spherical, thick-walled stomach at 

 its antero-dorsal border. The intestine and "terminal papilla" are 

 also longer than in the younger specimens. The swimming is more 

 active and the larvae are not confined to the surface of the water, but. 

 pass frequently to the bottom of the vessels in which they are kept. 

 Many of the specimens of this age, as was also true of the younger 

 ones, had masses of ingested matter in the stomach. The larvae 

 may, besides the rotation and forward motion, swim rapidly in a 

 circle with the pre-oral lobe and body flexed dorsalwards. They 

 may be kept alive in aquaria for six or seven days longer but do not 

 develop further, in spite of one's effort to feed them on diatom cul- 

 tures. To this point my observations on the development of the 

 trochophore agree with those which E. B. Wilson made ('83) on 

 larvae reared from the artificially-fertilized eggs. 



That the larvae may be reared from eggs in aquaria by the use of 

 some suitable method of providing them with animal food is sug- 

 gested by the rapid growth of a single lot of larvae during the sum- 

 mer of 1905. Several hundred larvae that were two days old were 

 transferred to an aquarium containing a luxuriant growth of diatoms 

 (Grave's diatom method) and placed several feet from a window to 

 avoid direct sunlight. When they were six days old the larvffi 

 exceeded in size and development even the oldest specimens of 

 earlier cultures. They were 1 millimeter long as compared with 0.6 

 millimeter for the dwarfed (and underfed) larvae reared in ear- 

 lier cultures. They formed a connecting-link between those just 

 described and the youngest from the tow. The larvae contained many 



