102 SYNOPTIC COLLECTION. 



so far as our knowledge goes, is not true of Protohydra 

 or Hydra. In the hydro id state Microhydra is greatly 

 reduced, since it possesses neither chitinous coat nor ten- 

 tacles, and is also without a pedal disc. According to 

 Potts this species was found living as a messmate among 

 colonies of Bryozoa " where its own disabilities as a food 

 collector .... were supplemented by the life sustaining 

 currents induced by its more active neighbors." This 

 habit has doubtless brought about this reduced structural 

 condition. 



The marine and fresh-water Protohydra of Greef is rep- 

 resented by Pis. 124 and 125. It is less reduced than 

 Microhydra, by possessing a chitinous coat and by living 

 in both salt and fresh water, but, like this genus, it is with- 

 out tentacles. PI. 124, fig. i represents Protohydra con- 

 tracted into a spherical form. Its color is a fox brown. 

 Fig. 2 shows the little animal in the act of stretching out, 

 and in figs. 3 and 4 it is still more extended. In the lat- 

 ter figure the mouth is seen at the top and the foot disc 

 at the posterior end. Fig. 5 is a Protohydra that has 

 swallowed a Copepod larger than its own body. The long 

 bristles at the posterior end of the crustacean extend from 

 the mouth. Inside the hydroid the outlines of the Cope- 

 pod can be made out and also one of its red eyes. Fig. 

 6 is the forward end enlarged, showing the edges of the 

 mouth without even the vestiges of tentacles. Fig. 7 is a 

 portion of the body showing the network of cells. In 

 these figures the nearly colorless ectoderm is seen and the 

 underlying pigmented endoderm : no cuticle is repre- 

 sented excepting in fig. 8 (which is the posterior part of 

 a specimen that has been paralyzed in fresh water) where 

 it is visible outside of the cellular ectoderm. According 

 to Greef 1 this is most constant at the end of the body 

 where it has separated from the epithelium and surrounds 

 the body like a tube. Towards the forward end it lies 



1 Zeitschr. f. wiss. Zool., XX, p. 1070. 



