✍ Scribed by Segal, Earl
No coin nor oath required. For personal study only.
Since '05, when Simroth reported a humpbacked slug, there have been several reports of humps or tumors at the posterior portion of the mantle shield of sluglike, terrestrial, pulmonate gastropods (Szab6 and Szab6, '31, '34; Fromming, '54; Boettger, '56; Fromming et al., '61).
Many of these humplike structures have been shown, histologically, to be true tumorous growths; others have been shown to be tumor-like growths (the repair hyperplasia and cell hypertrophy of Scharrer and Szab6-Lochhead, '50). A third type of humplike structure has been observed in the slugs Limax flavus (From- ming, '54) and Deroceras reticdatum (Fromming et al., '61). Histological ex- amination of the hump of Deroceras showed that it is a dermal sac containing normal viscera (Fromming et al., '61).
These authors have referred to it as a hernial sac. They consider the hernial sac to be a local malformation brought about during the hatching process as the animal attempts to force its way through a too small opening in the egg shell. The visceral organs are thus displaced and remain in the extruded sac after hatching.
In the present paper it will be shown that : ( 1 ) Limax flavus may indeed hatch with portions of its viscera in a sac at the posterior edge of the mantle shield, but, this malformation appears while the animal is still in the egg and is the cause rather than the result of a difficult hatching; ( 2 ) the production of a hernial sac depends upon the incubation temperature; and (3) the location of the hernia is const ant and theref ore predictable.
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