Translation of the original German introduction by Ernst Haeckel:
Phylum of Mollusca (Weichtiere); - class of Gasteropoda (Schnecken); - legion of Prosobranchia (Vorderkiemer); - order of Ctenobranchia (Kammkiemer).
The speciose order of Ctenobranchia belongs to the legion of Prosobranchia; it includes the huge majority of those snails that are distinguished by delicate form and manifold coloration of its impressive spiral shell. The characteristic formation of this ambagious “snail house” into which the soft body can retreat completely, is effected by the asymmetrical growth of the latter. Of both ‘antimeres’ or ‘counterparts’ of the body which have originally been structured in a symmetrical way (so in the oldest snails) the left half grows stronger, the right side weaker (or the other way round). As a consequence the related organs of the “mantle-complex”, arranged in pairs (paired branchiae, pre-chambers of heart and kidneys), are regressed on one side, on the other all the more developed. At the same time the intestinal pouch, containing these and other organs, is rolled from the back of the left side to the front of the right side; consequently, the branchia that was initially lying behind the heart, now comes to lie in front of the heart. During further asymmetrical growth the intestinal pouch that protrudes from the back of the animal like a rupture is hoisted spirally, and the lime shell that segregates from the spinal skin takes the shape of an ascending spiral staircase (fig. 6-8). With lope-like or finger-shaped appendices emanating from the wrinkled rim of the ‘mantle’ (of the spinal skin) that again deposits lime covers, prickle- or wing-like appendices of lime shell develop giving the snail shells their specific and delicate form (fig. 1, 4, 5, 7, 8). Plate 53 illustrates lime shell of only few of the most beautiful Ctenobranchia; the soft body of the animal that fills the shell cavity is not seen.
Translation by VR Translators Bangalore
We've scanned the original lithography at 1200dpi on the Epson A3 scanner of A3 scanner huren. You can download a 400dpi JPEG here.