OBSERVATIONS OX POLYZOA. 215 



examination of this part, by transmitted light, to their junc- 

 tion with the body of the statoblast. From the edges of 

 the statoblast they pass through the centre of the annulus, 

 coming out on the border of the seam, that divides the up- 

 per and lower sides of the annulus. 



Prof. Allman describes the statoblasts of Cristatella as 

 surrounded by a ciliated envelope before the spines begin 

 to be developed, and remarks, that these impinge upon 

 this membranous envelope, which gives way before them 

 and disappears. I have been unable to detect any similar 

 ciliated membrane in Plumatella or Pectinatella, and, in 

 this respect, Cristatella probably differs from all the other 

 Phylactolgemata. The gelatinous matrix of the statoblast 

 of Pectinatella does not reach its full growth before the 

 spines are produced, but appears to be carried up on their 

 sides as they progress outwards. When the spines are 

 fully developed, the reentrant spaces in the envelope be- 

 tween them become filled out, and they are buried in the 

 gelatine, like those of Cristatella when they first begin to 

 protrude from the horny sheath. 



The gelatine is absent from the full grown statoblasts of 

 Fredericella and Plumatella, which are found naked in 

 the co3noecial cells, whereas those of Pectinatella and Cris- 

 tatella are enveloped by it until after the death of the colo- 

 ny; losing it only by decay. In the two first this covering 

 is not essential, and it is absorbed before the bud is floated 

 out of the ccenoecium, while in the two last it is needed in 

 order to protect the parent from laceration by the pointed 

 booklets of the spines, and it is, therefore, retained until 

 lost by the exposure of the bud to external influences. 



Before the spines of PectinateJIa appear, and often, even 

 before the horny casing shows the deeper shades of the 

 brownish coloring that afterwards distinguishes it, the stat- 

 oblasts are detached from the funiculus. They lie loose 

 in the coenoecial cavity from this time until the death and 

 decay of the polypides destroy the upper parts of the cells. 

 Through the openings thus made, being lighter than water, 

 they are readily floated off and pass the winter unprotect- 

 ed by any other covering than their cellular casings, al- 

 though remaining near the surface, and consequently, in 

 the higher latitudes, imbedded in the ice for several months. 



