XXX 



INTRODUCTION. 



shut one part within another, so as to admit of the head 

 being projected forward, that the animal might eat its 

 way into the wood that it penetrates." This we have not 

 been able to verify, nor can we see the necessity for the 

 disarrangement of the stomach with all its attachments, 

 when a prolongation of the cesophageal canal would 

 enable the animal to accomplish the work on far easier 

 conditions. 



The structure of the alimentary canal is longitudinally 

 fibrous. In the genus Ligia, a little anterior to the anal 

 termination, a series of transverse muscular bands sur- 

 round it without uniting on the under surface, and 

 probably fulfil the office of sphincter muscles. 



About two-thirds of the distance between the stomach 

 and the telson, one or two appendages are attached to the 

 alimentary canal in the Amphipoda. We say one or two, 

 because we have distinctly dissected out two in Sulcator 

 (Fig. 5), but have failed to determine more than one in 



FIG. 5. 



Gammarus (Fig. 6), Mcera, and other genera. The organ 

 is free at one extremity, and is borne in a forward posi- 

 tion, resting on the dorsal surface of the primavia. It 

 is more important in appearance in some Amphipoda than 

 in others; in Sulcator it is very long. We have never seen 

 it in any of the Isopoda that we have examined, but, as far 

 as our experience supports us, it is present both in the 

 male and female Amphipoda, in the adult as well as in the 



