348 J. M. D. OLMSTED 



3. Synaptula hydriformis shows decided physiological polari- 

 zation, since it always moves with the anterior end foremost, 

 and keeps its dorsal side uppermost. 



4. Carmine powder fed to specimens 6 cm. in length appears 

 in the foeces after about 20 hours. 



5. The food of Bermuda specimens consists chiefly of a fila- 

 mentous (red?) alga. 



6. The temperture coefficient for the rhythmic pulsation of the 

 intestine obeys the R. G. T. rule. 



7. The intestine beats normally in artificial sea-water, and 

 for a much longer time in a balanced solution of Na, K and Ca 

 salts than in any other combination of the components of sea- 

 water. NaCl is the only single component of sea-water in 

 which peristaltic movement of the intestine continues at all. 



8. Nearly every Bermuda specimen contains a mass of sym- 

 biotic bacteria lying free in the body-cavity. 



9. The red and green varieties show no difference in their 

 sensory reactions. 



II. SENSORY PHYSIOLOGY 



1 . The effect of deforming pressure 



a. Historical. The so-called 'touch-papillae' or 'sense-buds' 

 are found in abundance on the tentacles of Synaptula hydrifor- 

 mis, but they are scattered over the surface of the body as well. 

 Clark ('07, pp. 47, 48) describes them as "small groups of epi- 

 thelial cells connected at their inner ends with special ganglia 

 situated at the ends of small nerves, which arise as branches of 

 either the radial or tentacle nerves." "The senory cells are 

 much more elongated than the ordinary epithelial cells, and the 

 inner end is drawn out into a fiber which connects directly with 

 the small ganglion lying underneath the sense-bud." Retzius 

 ('06), who made a study of the sensory cells of Synapta Buskii, 

 finds the same structure and distribution of the sensory cells in 

 this species. Semper ('68, p. 28, p. 153) — not Hamann ('83), as 

 stated by Clark ('98) — seems to have been the first to describe 

 such papillae in Synaptidae, and to suggest that they were 



