147 
will not help us at all, and will explain nothing, unless it be accounted 
for by other facts, and not by mere hypotheses !). 
The present grouping is false?), because it is not in harmony 
with the facts to be presently mentioned. 
1) In the „Theorie des Mesoderms“ (Morph. Jahrb. Bd. XV, p. 155) 
Rast writes: „Man hat aber bisher, wie mir scheint, ein ungemein wich- 
tiges Moment, wenn auch nicht gerade übersehen, so doch wenigstens viel 
zu wenig beachtet: ich meine die wiederholte Erwerbung und den 
wiederholten Verlust des Nahrungsdotters während der Phylogenese.“ 
Whence did Rast get this information? Not from the facts of Ver- 
tebrate morphology, but by that use of the scientific imagination, which 
enables him to evolve Ganoids from Selachians, and more wonderful still, 
Dipnoans from Ganoids. It is heaping hypothesis on hypothesis to talk 
of secondary and tertiary „dotterarme“ eggs. It the eggs of a form once 
lose the yolk they have acquired, some cause must be at the bottom of 
that loss; the only cause which has ever operated to that end appears to 
me to have been intra-uterine development. Ihe one loss was the final loss. 
I have shewn in this essay that the Ichthyopsida, when naturally arranged, 
negative this supposed repeated loss and gain of food-yolk; it would be 
a comparatively simple matter to extend this negation to the remaining 
Vertebrata by showing that the eggs of their ancestors must have pos- 
sessed the three stages holoblastic (Amphibian ancestors of Amniota), me- 
roblastic (Reptilian ancestors of Amniota, and still persistent in Monotremes), 
and of gradual loss of food-yolk as a consequence of the initiation of 
uterine development. 
What shall one make of Rast’s assurance that „der ganze Verlauf 
der Gastrulation so sehr zu Gunsten der Ansicht, daß ontogenetische und 
phylogenetische Reihenfolge einander entsprechen (spricht), daß sie un- 
möglich von der Hand gewiesen werden kaun“? In plain words, our author 
sets up an hypothetical pedigree of the Vertebrata, based on not one but 
a series of hypotheses, then by means of another series of hypotheses he 
shows that the gastrulation conforms to his first hypothetical schema! 
Rast seeks to prove the evolution of the Vertebrata from Amphi- 
oxus-like forms; many of the facts he records, and indeed, the general 
descriptive part of his work, shew great care and much labour, but the 
facts are made to fit the schema and the inconvenient ones, (always the 
statements of some other, often incompetent, observer!) are ignored or 
turned aside. Shall we not apply to Raxt’s hypotheses the judgment he 
has given on almost all others (fast simtliche) that his schema is ,,eine 
Beweisführung um jeden Preis, selbst um den Preis der Thatsachen“? 
2) False as a phylogenetic arrangement. When that great morpho- 
logist, Jonannes MÜLLER, classified the fishes as Dipnoi, Teleostei, 
Ganoidei, Elasmobranchii, Marsipobranchii and Lepto- 
cardii (Bau und Grenzen der Ganoiden, p. 85—88), he undoubtedly 
created a more scientific system that the one then in vogue due to L. 
Acässız; but MÜLLER never dreamt that his grouping would be made the 
basis of a phylogenetic creed! Haxcket, Rast and others have converted 
Mtıter’s system to uses for which it was never intended by its author! 
10* 
