292 



ERNEST WARREN. 



As a rule the stem is perfectly straight, and only rarely is it 

 slightly zig-zag. 



At the origins of the stems and branches there is frequently 

 an annulation of 3-4 rings. 



Diameter of stem, measured a short distance above its 

 origin from the hydrorhiza, 0'278 mm ; thickness of perisarc 

 38 ^I. 



Text-fig. 5. 



A and B. Sei-tularellapolyzoiiias (Lin.). X 18. C and D. 

 Sertularella fnsiformis {HiHcTis}. x 18. 



Hydrotheca. — Alternate, ventricose beloAv, contracted 

 above, divergent, expanding mouth. About one half is sunk 

 in the hydrocaulus. The mouth is quadrangular and provided 

 with four teeth at the angles, two of which are lateral, one 

 adcauline, and one abcauline. 



•» Three internal knobs of chitin, constricting the size of the 

 mouth, are usually developed near the edge ; two are placed 

 in the middle of the two sides of the square on the adcauline 



