
No. 426.] THE CILIATED SPONGE LARVA. 453 
times less the diameter of the mature gemmule, are however 
present, although not common, in the parent parenchyma. 
My conclusion that a larva, identical in structure with the 
typical egg larva of the group, is produced asexually in the 
manner just indicated has not seemed to certain reviewers 
(Maas,! Minchin?) altogether worthy of credence. And it may 
be that subsequent researches will show that such a conclusion 
is not necessitated by the facts. What I may point out here, 
however, is that the conclusion rests upon a series of micro- 
scopic pictures, the arrangement of which is left to the intelli- 
gence of the observer, and that this is precisely the kind of 
evidence on which rests our belief that in other sponges an egg 
development occurs. If, to be sure, the microscopic pictures 
(images) have been portrayed by me in an inaccurate fashion, 
then there is no need to consider the logic involved in their 
arrangement. This is in reality the point of view from which 
Maas has criticised my account, although he professes to find 
in my figures evidence for the correctness of his interpretations 
of them. Maas, in short, very freely and confidently expresses 
(98, p. 370 ; '96, pp. 233—234) the belief that the bodies I figure 
and describe as gemmules are merely eggs surrounded by masses 
of nourishing cells ; and that the dissolution of the mature 
gemmule into subsidiary masses and ultimately into separate 
cells is only the segmentation of the egg. This process of dis- 
solution specially awakens his incredulity: * Wie man es sich 
vorstellen soll, und welche Kräfte es bewirken sollen, dass ein 
Aggregat von Zellen, eine Gemmula, sich in einzelne Stücke 
weiter und weiter spaltet, darnach will ich hier nicht fragen, 
sondern nur darnach, warum Wilson in dem ganzen Vorgang 
nicht eine Furchung, in dem Auseinanderbrechen der Massen 
in kleine und kleinere Stücke nicht eine Zellteilung gesehen 
hat!?'" (96,p.234). The mechanics of the process to me seem 
unworthy of so much wonder. Absorption of water by the 
1 Die Embryonal-Entwicklung und Metamorphose der Cornacuspongien, Zai. 
Jahrb., Abth. f. Anat. und Ontog., Bd. vii, 1893; Erledigte und strittige Fragen 
der Schwammentwicklung, Biol. Centralbl., Bd. xvi, Nr. 6, 1 96. 
2 The Position of Sponges in the Animal Kingdom, Science Progress, vol. i, 
N.S., July, 1897. 
