464 



APPENDIX 



Expt. 9. The next specimen is Tubifex, a multicellular round-worm 

 living everywhere in the mud at the bottom of ponds, ditches, etc. 

 Easily seen with the naked eyes, use objective No. 3 to study the often 



FIG. 256 



Daphnia pulex, De Geer: 1, antennules; 2, left antenna (the right not being shown); 3, man- 

 dible; 5 to 9, gill-feet; 6, embryos in the brood-sac; g, brain; go, optic lobe with the eye above 

 it; h, heart; k, e, o, various stages in the degeneration of the aborted eggs into food within the 

 intestine. The long spine at the lower dorsal corner is a means of defence after the animal has 

 dived into the silt at the bottom. The curved claw-like projection in front and below is used 

 for removing intruding objects from without. (Hertwig.) 



transparent protoplasm of this animal. Note especially near the pos- 

 terior end a large slowly pulsating dorsal artery about the first observed 

 sign of a heart as one looks "upward" in the animal " series." Make 



