OBSERVATIONS ON FRESH-WATER POLYZOA. 



141 



thelinm. A glance at fig. 56, PL XX. will make this clear. The 

 middle portion of this mesentery-like membrane becomes thinner, 

 and is finally perforated as shown in fig. 57, PI. XX. The sac is 

 then joined to the cystidal endocyst at two points, viz. at its opening 

 and at the bottom. Rndiments of new buds are produced in the region 

 lying between these two points, which separate more and more from 

 each other. 



The solid rod-like part of the lining epithelium whirh now joins 

 the bottom of the sac-shaped bad witli the cystidal wall, is the rudi- 

 ment of the funiculus. It gradually lengthens, and a lumen is 

 secondarily formed in it, turning it into a tubular organ. It grows 

 in size, and with the eai'ly appearance of scanty muscular fibres inside 

 its cavity the development of the funiculus is complete. Thus the 

 result of my observations on the formation of this organ seems to 

 agree essentially with tliat of Bra^m (2) wIkj describes the process in 

 the following w^n-ds : " In der Mediane erheben sich die Zellen des 

 äusseren Blattes in Gestalt einer an der Oralseite der Primärknos])e 

 herablaufenden Längsleiste, welche seitlich von den Fortsetzungen 

 der Magenfalten begrenzt erscheint. Indem sich die Zellen des 

 Knospenhalses dann nacli vorn umschlagen und an der Bildung des 

 Integuments betheiligen, löst diese Leiste sich von dem Mutter- 

 gewebe, welclies hintei- ihn zusammenfliesst, als selbstständige Strang 

 los und verdindet einen oral und median vor dem Primärknospe 

 gelegenen Pimct der Leil)eswand mit dem Grunde des Knospen- 

 Sackes. 



A constricti<^n is formed in the middle part of the sac-like bud, 

 dividing it into two chambers. The constricted opening is the mouth 

 of the future ])«>ly|>id(', and the lower chamber developes into the 

 alimentarv canal. The upper (-hamber becomes somewhat conical in 

 shape tapering toward the orifice of the bud. At the basal disc of 



