402 



INVEKTEBEATA 



CHAP. 



preserved his paralysed larvae in a mixture of the solution of cor- 

 rosive subUmate and glacial acetic acid, or in Fleming s fluid. 



The best account of the metamorphosis of the larva we owe to 

 Harmer (1887). He found that he could not get the larvae which 



muse 



comm 



Fig. 320. 



-Optical sagittal section of the free-swimming larva of Pedicellina echinata. 

 (After Czwiklitzer combined from several figures. ) 



a, anus; a.c, anal cone; aj^, apical plate; ap.g, apical ganglion cells; at, atrium; co, corona; 

 comm, nervous commissure ; d.o, dorsal organ ; ep, epistome ; hep, dark granular endoderm cells con- 

 stituting the so-called liver; int, intestine ; m, mouth ; muse, muscle fibres ; neph, excretory organ ; 

 sb.og, sub-oesophageal ganglion ; s.o.g, cerebral ganglion ; st, stomach. 



swarmed out from the vestibules of the parent colonies to fix them- 

 selves to the walls of the vessels in which he had placed these 

 colonies ; so he resorted to the following device. He procured 

 colonies of Pedicellina echinata fixed to the calcareous seaweeds 

 known as Corallines. He cut off all the superfluous branches of the 

 coralline and placed the pruned stocks carrying the 'Pedicellina in 



