verify, except those of the short resume we have given 

 from Patten with regard to the development. 



It is unnecessary to refer to the many autliors wliose 

 works we have had to consult, hut we Avish to acknowledge 

 our special indebtedness to. the researches and theories 

 of Eay Lankester, T. W. Spengel, Pelseneer, Pemy 

 Perrier, Bela llaller, Jj-acw/.o Duihiers, lioutan, Orol)l)en, 

 and Patten. 



The matter which wq helieve io he new includes the 

 following' fdiief points: — 



(1) A lateral glandular streak has heen found along 

 each side of the foot of young specimens, resembling ihat 

 found in Nacella and its allies. 



(2) A muscular zone (which we name tlie internal 

 pallial muscle) has been found extending in the mantle 

 between the tips of the shell muscle. 



(8) The structure of the Crop, and inferences drawn 

 therefrom as to special torsion of the viscera of Drvoglossa 

 during consolidation of the visceral hump. 



(4) The respiratory function of the nuchal cavity as 

 regards damp air. 



(5) Discussion of the evolution of the present topo- 

 graphical relations of rectum, kidneys, pericardium, and 

 lieart. 



((I) Details of mantle innervation and pallial tentacles. 



Our best thanks are due to Professor AV. A. llerdman, 

 D.Sc., F.II.S., the Editor of this series, for his general 

 advice and special suggestions, and to Prof. J. Travis 

 Jenkins, D.Sc, Ph.D., late of Aberystwytli, for woiking 

 out several intricate details of mantle innervation as well 

 as other points. The greater number of the drawings aie 

 original, but a few are based on those o-iven in Lankester's 

 articde " Mollusca," in the l-hicyclopa'dia Britannica fOth 

 edition), and those of the devcdojiment are afler Patten. 



