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epidermis, but HevBrecnT considers the outer ectodermal layer 
(Deckschicht) such as especially anuran larvae show it, as a 
separate organ, a reduced larval envelope. If this view were correct, 
we should expect this larval envelope to be developed in an obvious 
way in Gymnophiona and primitive tailed Amphibians such as 
Amphiumidae (Megalobatrachus, Cryptobranchus) and Proteidae 
(Necturus), whose eggs pass moreover through a long embryonic 
period, and this is in no way the case. In these forms the two 
layers of the epidermis bear exactly the same histological character. 
The solid ingrowth of cerebral ganglia seems to originate out of 
the deeper nervous layer only, but even this may be delusive. The 
invagination of the neural plate takes place before the differentiation 
of the two layers, or both participate in it. The extraordinary 
development of the ‘“Deckschicht’ in tadpoles may be partially 
ascribed to the fact that in these forms this layer forms a number 
of temporary organs possessing great importance for the subsistance 
of the larva, such as the suckers ventral to the gillregion and 
the larval sucking-mouth with its horny teeth, while perhaps the 
outgrowth of the operculum requires more material from the epi- 
dermis than in Urodelan Jarves without this cutaneous fold. 
Another weakness in Husprecut’s theory is the fact that it gives 
no conclusive explanation of the differentiation of the holoblastic 
Amphibian egg into the embryonic knob and the exembryonic fruit- 
bladder of Mammals. As Husrecurt starts from eggs without or 
with a small amount of yolk >, this important question remains 
unsolved. Husprecut has paid little attention to this point. On p. 36 
Le. 1895 he writes: 
‚Nun lässt es sich denken, dass Formen welche in diese zweite 
“Kategorie gehört haben mögen, nebenbei eine starke bruchsackartige 
“Erweiterung der Bauchwand erlitten haben, und dass die Bildung 
“des Bruchsackes mit der eben erwähnten ringformigen Einpflanzungs- 
“linie des primitiven Amnions zusammentiel”. 
p. 56: “Es ist viel wahrscheinlicher, dass die Protamnioten vivipare 
*Amphibien gewesen sind, bei welchen, durch Flüssigkeitsansammlung 
“zwischen den Hypoblastzellen eine prall gefiillte, pseudomeroblastische 
“Keimblase zu Stande gekommen ist”. 
1) ] will remark on this point that in Huprecut’s writings the terms “dotter- 
arm” and ‘‘dotterreich’’ are often used, when he really means holoblastic and 
meroblastic. Of course the existence of holoblastic eggs with an enormous amount 
of yolk such as in Amphiumidae, Gymnophiones, Necturus, Dipnoi, Ganoïds 
etc. and of meroblastic eggs with a rather small amount of yolk, such as pelagic 
Teleostean eggs, was known to him, but these eggtypes orly play a subordinate 
part in his theoretical reasoning, 
