PLATE XXIX 

 TYPICAL MOLLUSCAN EMBRYOS 



1. Craspedochdus cinereus, Linn. [Polyplacophora.] Showing the 

 shelly plates which are retained in the adult state. (After Loven.) 



2. Myzomenia Banyulensis, Pruvot. [Aplacophora.] Showing the 

 shelly plates which are lost in the adult. (After Pruvot.) 



3. Rissoia costata, Desm. [Gastropoda: Prosobranchia.] (After 

 Loven.) 



4. Embryo of unknown Prosobranch, with four-lobcd velum. 



5. Favorinus branchialis. [Gastropoda: Nudibranchia.] Showing 

 nautiloid shell and operculum discarded in the adult state. (After 

 Loven.) 



6. Dentalium Taventinum, Lamk. [Scaphopoda.] (After Lacaze- 

 Duthiers.) 



7. Ostrea edidis, Linn. [Pelecypoda. j Lateral view, seen through 

 the shell. (After Huxley.) 



8. Modiolaria marmorata, Forbes. [Pelecypoda.] (After S. P. 

 Woodward.) 



9. Anodonta sp. [Pelecypoda.] Formerly considered a distinct 

 animal, and called Glochidium. (After Forel.) 



I Sepia officinalis, Linn. [Cephalopoda.] Two stages in its 

 " - development (after Koelliker). The rounded body to which 

 I it is attached is the yolk-sac. 



In the foregoing Figs. : a., arms ; e., eye ; /., foot ; fn.. fin ; in., mouth ; 

 ma., mantle; 0., operculum; s. , shell; v., ciliated velum. 



12. Diagrammatic sketch of the structure of the eye in — A , Oigopsid 

 Cephalopod ; B, Gastropod (Helix, Limax, etc.) ; C, Nautilus, Patella 

 (after Grenacher) : c. , cornea ; i.e., inner cavity ; int., integument : w..\ 

 iris; /. , lens; /'.. outer portion of lens; o.c., outer cavity : op.g., optic 

 ganglion ; op.n., optic nerve ; v., retina. 



13. Openings of the siphons of the common cockle {Cardium edule, 

 Linn.), showing the fringes of tentacles bearing ' ' eyes. ' ' (After Mobius.) 



14, A~C. Successive stages in the growth of a young Fissurella, 

 showing the transition of the anal notch in the margin of the young 

 shell into the apical anal aperture in the adult. (After Lang.) 



15, A-C. Successive stages in the growth of a young Anomia, 

 showing the conversion of the ventrally placed byssal notch (b.) into 

 the umbonal byssal opening of the adult by the growth round the 

 shelly byssus of the shell itself. (After Morse.) 



*„.* Drawn by Miss G. M. Woodward. 



