198 HYATT, 



since, as previously noticed, Lophopus forms an interme- 

 diate step to its passage under the coeuoecium in Pectin- 

 atella. 



CCENCECIAL ENDOCYST. 



Cells of the first membrane small and dej)ressed. This 

 character, and its subsequent change to the larger cells of 

 Pectinatella and Cristatella, was described in the article 

 on the " Composition of the Body." It is due, perhaps, 

 to the removal of the pressure of the superincumbent 

 ectocyst from the upper side of the coenoecium. 



Cells of the second membrane small. This character, 

 which appears to be invariable, may possibly owe its 

 equability in the size of the cells to the equal pressure of 

 the other membranes on either side. 



The remaining characters need no explanation until we 

 reach 



FEEE STATOBLASTS. 



Bean-shaped, depressed, or elongated ellipses. The va- 

 riability of the statoblast, as will be seen in the descrip- 

 tion of the species, becomes less in Plumatella, and is of 

 fixed value in Pectinatella. 



The depressed elliptical forms are in reality orbicular 

 forms, or are those varieties which assume a close approx- 

 imation to the outline finally taken by all the free stato- 

 blasts of Cristatella. 



Thus it may be said of the three forms which begin 

 as varieties in Fredericella, of which the bean-shaped is 

 perhaps the most .common, that they all successively cul- 

 minate in some one genus, and then die out. Thus the 

 bean-shaped disappears in Plumatella, the elliptical takes 

 its place in the latter and in Pectinatella, and the orbicular 

 form, which only holds a place in the varieties of the dif- 

 ferent species of the preceding genera, at length predomi- 

 nates and is characteristic of the genus in Cristatella. 



EECAPITULATION OF THE CCENCECIAL SYSTEM. 



The synopsis itself sufficiently explains the remaining 

 characters of this system, and we may, therefore, proceed 



