218 



Fig. 53. Diagraminatic representation of a section of the body wall of Spon- 

 gilla (with few alterations after Delage and Hérot-ard). cnli. = 

 conukis; p. = ostia; os. = osculuin; ox.t. = oscular tube; ects. 

 = ectosome; cv. hij. = subdermal cavity; en. inh. = incurrent 

 canal; cn.exh. = excurrent canal ; c/^s. = parenchyma ; the arrows 

 indicate the direction of the water current. See p. 119 — 120. 



Fig. 54. Fiagellated chambers and surroundings in Spongilla. fl. ch. = 

 flagellated chamber; inc. can. = incurrent canal; exc. can. = 

 excurrent canal. Magnif. ih 130 times. The arrows indicate the 

 direction of the water current. See p. 120. 



Fig. 55. Section of a flagellated chamber of Spongilla (magnif. + 1600 times), 

 after Vosmaer and Pekelharing, ap. = apopyle. See p. 120. 



Fig. 56. Successive stages of the flagellar movement of an isolated choa- 

 nocyte. The cell body is still connected with several other choa- 

 nocytes, the collar is entirely retracted. The arrows indicate the 

 direction of the water current, the dots floating particles; the 

 moment of observation is given in each case; a. immediately 

 after isolatiou; in e. the flagellum bas finally come to rest. Magnif. 

 rb 1770 times. See p. 126—127. 



Fig. 57. As Fig. 56. The collar is partly retracted. a. immedately after 

 isolation; in c. the flagellum lias come to rest; in d. — e. a (new) 

 period of weak motion began again, which is fmished in /". Magnif. 

 ± 1770 times. See p. 128. 



Fig. 58. Successive stages of the flagellar movement of a number of cho- 

 anocytes still joined within a part of a flagellated chamber, 

 observed in a i"avel preparation. The collars are entirely retracted. 

 a. im-mediately after isolation, in c. the flagella have finally come 

 to rest. Cnf. Figs. 56—57. See p. 128, 132. 



Fig. 59. Intact tlagellated chamber of living Spongilla grown on cover- 

 glass; the flagella in the normal spiral- or undulating-niotion. 

 The collars are fuUy expanded. ch.l. = choanocytic layer; odr. = 

 oildrops. Magnif. ± 1430 times. See p. 130 — 131. 



Figs. 60 — 62. Representation of flagellum and collar seen on top; in Fig. 60 

 the tlagellum stops, in Fig. 01 it is in spiral-motion, in Fig. 62 in 

 flat undulating-motion. See p. 131 — 132. 



Fig. 63. Diagrammatic representation of the water current inside a flagel- 

 lated chamber of Spongilla. pr.p. = prosopyle; ap.p. = apopyle; 

 the arrows indicate the direction of the current; + and — refer 

 to the water pressure. See p. 132 — 134. 



Fig. 64. Semi-diagrammatic rei)resentation of a chamber, the flagella of 

 which are beating with the tops outside the apopyle. ch. l. = 

 choanocytic layer. See p. 135 — 136. 



Fig. 65. The dill'erent ways of capturing (food-)particles within a flagel- 

 lated chamber of Spongilla (diagrammatic). The prosopyles have 

 not been drawn, nor the separate cells of the choanocytic layer 

 (c/l. l.). The way taken by the particles is indicated by dots. 

 a. and b. show the capturing between the bodies of the choano- 

 cytes; c. the capturing between the collars; d. the capturing at 

 the bases of the collars, See p. 143—145. 



