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HANDBOOK OF INVERTEBRATE ZOOLOGY. 



microscope, and allow it to remain undisturbed for ten or 

 fifteen minutes. The soft parts of a tightly-closed speci- 

 men are so crowded together inside the shell that it is dif- 

 ficult to study them, and almost as soon as a specimen is 

 fully expanded, it rises from the bottom and swims away 

 by the motion of the cilia of the velum, but a little pa- 

 tience will probably lead to the discovery of half-expanded 

 specimens, and these can be examined without much dif- 



Fio. 173. 



FIG. 173. Right side of swimming larva, or Velic/er of Montacuta 

 ferruginosa, greatly magnified. (Copied with slight changes, from Love"n, 

 " Ent. dcr MolhiKca Acephala Lamellibranchiata," Fig. 104.) 



D. Dorsal surface. V. Ventral surface. A. Anterior end. P. Poste- 

 rior end. o. Shell, a'. Hinge, aa. Anterior adductor muscle, b. Body 

 cavity, c. Ear. /. Flagellum. L Intestine. I. Liver. ?n. Mantle. 

 oe. (Esophagus, cv. Cilia of velum, v. Velum, vm. Retractor muscles 

 of velum. 



ficulty. The larvse will probably belong to several species, 

 but most of those which are captured at the surface are 

 sufficiently like Fig. 173 for the student to make this figure 

 his guide in studying them. 



