227 



richtetes Läppchen (Fig. 2, ì). Der Vordeirand dieses Läppchens ist 

 mit vier Zähnchen besetzt. 



Der Außenrand des genannten Stielghedes ist mit einem kräftigen 

 Dorn versehen. Vom Läppchen bis zu diesem Dorn hin zieht sich ein 

 Borstenrand; ebenso ist das AntennengKed auch oberhalb des vier- 

 zähnigen Läppchens mit Borsten besetzt. 



2. The relation of the flagellum to the nucleus in the collar-cells of 

 calcareous sponges. 



By E. A. Minchia, London. 

 'Witli6%s.) 



eingeg. 18. Okt über 1909. 



In former memoirs i I have divided the Calcarea Homocoela or 

 Ascons into two families, Clathrinidae and Leucosoleniidae, and 

 amongst other characters which distinguish these two groups, I pointed 

 out that in the Clathrinidae the collar-cells have the nucleus basal, 

 while in the collar-cells of Leucosolenidae the nucleus is apical in 

 position. I expressed the further opinion that the ordinary Heterocoela, 

 such as Sjjcoii, are more nearly related, systematically and phylogene- 

 tically, to the Leucosoleniidae than to the Clathrinidae, and 

 that they also exhibit the apical position of the nucleus in the collar- 

 cells. 



In the investigations on the histology and developement of Sycon 

 raphmius recently published by Dr. E. Hammer^, the author points 

 out that in the collar-cells of this sponge the position of the nucleus 

 is so variable that it cannot have any systematic or phyletic value »Die 

 Lage des Kernes ist jedoch, wie ich glaube, trotz einer gewissen Eegel- 

 mäßigkeit eine so variierende, daß man ihr systematische bzw. phyle- 

 tische Bedeutung im Sinne Min chins nicht beimessen kann« (p. 323). 

 The same criticism of my views has been expressed by my friend Prof. 

 A. Dendy, both in com^ersation and in discussions at the scientific 

 meetings of the Zoological Society of London. I am prepared to acknow- 

 ledge the validity of the criticism so far as it goes; the fact of the matter 

 is that the distinctive feature of the two types of collar-cells in question 

 should have been stated by me in a different manner. The important 

 point is not the exact position, apical or basal, of the nucleus in the 

 collar- cell, but the relation of the nucleus to the flagellum, a relation 

 of which the position of the nucleus is but a secondary consequence. 



1 See especially Lankester's Treatise on Zoology. Part II. 1900. Chapter 3. 

 p. 56 and 109, 110. 



2 Xeue Beiträge zur Kenntnis der Histologie und Entwicklung von Sycon ra- 

 phanus. Arch. f. Biontologie IL p. 291-334. Tab. XXIII— XXVIII. 



15* 



