vorify, except tliose of the short resume Ave have o-lven 

 from Patten witli regard to the devehipmeiit. 



It is uiiiiecessary to refer to the many aiitliois wliose 

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

 our special indebtedness to the researches and theories 

 of 17ay Lankester, J. AV. Spengel, Pelseneei', I'emy 

 Perrier, ]iela iraller, Lacaze Dulhiers, l^oulan, (irohlien, 

 and Patten. 



The matter which we helieve lo be new includes llie 

 following- chief points: — 



(1) A lateral glandular streak has been found along 

 each side of the foot of young specimens, resembling tliat 

 found in Naeella and its allies. 



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

 pallial muscle) has been found extending in the mantle 

 between the tips of the shell muscle. 



{'■\) The structure of the T'rop, and inferences drawn 

 therefi'om as to special torsion of the viscera of Docoglossa 

 during consolidation of the visceral hump. 



(4) The respiratory function of the nuchal cavitv as 

 regards damp air. 



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

 graphical relations of rectum, kidneys, pericardium, and 

 heart. 



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



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

 D.Sc, F.P.S., the lulitor of this series, for his general 

 advice and special suggestions, and to Prof. .1. Travis 

 Jenkins, D.Sc., Ph.D., late of Aberystwyth, foi- working 

 out several intricate details of mantle inneivation as well 

 as other points. The greater number of the diawings are 

 original, but a fcAv are based on those given in Lankester's 

 article '" ^follusca," in the luicyclopai'dia Britannica (!)th 

 edition), and those of the deveh^pment are after Pallen. 



