60. 



S U M M A E. T. 

 A brief statement of tiie cliief points is as follov/s : 



ANATOm AST) PIABITS. 



1. Tlie mantle lias two pairs of sense organs, figiii'es 1, 

 ae, and pe, one long unpairel tentacle, st, and a fringe of 

 meirginal tentacles. All of tJiese organs are sensitive to me- 

 clianical st imiulation. The iinpaired tentacle seems to be liomol- 



ogeous to one of the ordinary marginal tentacles. 



2. The foot, figures 3 and 9, f, is a highly m odified bur- 

 rowing organ. 



3. The palp-appendages, figures 3, 10 and 18, pap, are food- 

 collectors. In tlie adult they are not assisted, to any consid- 

 erable extent, by any other organ. 



4. The gills, figures 3, 19 and 20, are used in pumping 

 water, for which function they are well fitted by their structure. 

 They probably servo in respiration but do not secjn to aid in col- 

 lecting food. 



5. Each genital duct, figure 29, gd, joins the outer, not 

 the inner, end of tlie corresponding excretory organ, very near 

 its op^iing into the branchial chamber. 



6. No division into cerebral and pleural gan.gliaha3 been 



