34 BULLETIN OF THE 



10. Role of the Mesodermal Vacuolated Cells. 



Allman ('56, p. 36) observed that at the time a lateral branch was 

 well formed, and before the origin of the polypide, the internal outline of 

 the body wall was uneven, and he figures (Plate XL Fig. 4) very large 

 cells lying on the inside of the body wall. Korotnefi" ('74, Taf. XII. 

 Figs. 1-3, '75, pp. 369, 370) progressed a step fai-ther, and recognized 

 a distinction between large, coarsely granular cells projecting into the 

 cavity of the bud, especially near the tip, and the surrounding epithelial 

 cells. Braem ('90, p. 126), finally, has described them more accurately. 

 He finds cells filled with numerous granules in the youngest branches of 

 the colony. Immediately around the bud, such cells are less abundant ; 

 probably, he says, because their granules have been absorbed in the 

 process of formation of the polypide. He compares the granules with 

 the yolk spherules of the statoblast cells, and believes that they are to 

 be regarded as food matter. 



My observations and conclusions, achieved independently of Braem's, 

 fully confirm his. I have succeeded, moreover, in obtaining some addi- 

 tional evidence as to the function of these cells, a subject to which I 

 have paid some attention. 



First as to the distribution of the cells, and their frequency in diffei'ent 

 regions. We can best get an approximate idea of this by counting the 

 number of the reticulated cells in each section of a series which in- 

 volves a young polypide and the regions immediately above and below 

 it. It is not possible to do this with perfect accuracy, because there is 

 no sharp line of distinction between reticulated and non-reticulated cells ; 

 but I have made the count without prejudice, and I believe as fairly as 

 possible. When the bud of the polypide has reached about the stage 

 shown in Plate III. Figure 28, the number of reticulated cells seems to 

 have nearly reached a maximum. In the series from which this figure 

 was taken there was an average of 4.8 reticulated cells to the section in 

 the ten sections distal of the bud. There was an average of 11.2 reticu- 

 lated cells to the section for the twenty sections which passed through the 

 bud, and 11.2 for the eleven sections proximal of the bud in the region 



perforated organs have been described by Smitt ('67, p. 426), Nitsche ('71, pp. 

 420-422), and Vigelius ('84, p. 26) for Flustra, by Freese ('88, p 7, 13, 14) for 

 Membranipora, by Ostroumoff ('86% p. 13) for Lepralia, by Claperede ('70, p. 160) 

 for Bugula and Scrupocellaria, by Eblers ('76, p. 14) for Hypophorella, and by 

 Joliet ('77, p. 222) for Bowerbankia. Nitsche alone ('71, p. 455) has had anything 

 to say upon their origin, and this apparently not the result of direct observation. 



