THE ANATOMY OF ALOYONIUM DIGITATUM. 387 



myo-epithelial cells; g. probably represents a group of epithelial cells from the 

 dorsal mesenterial filament ; ^. is a cnidoblast, but it is not possible to assert 

 that it belongs to the endoderm, as they were not seen in situ in the endo- 

 derm in any of the sections. 



Fig. 29. — A portion of the epithelium of the siphonoglyphe. 



Fig. 30. — Two nematocysts after they have been exploded by the action of 

 dilute acetic acid. 



Fig. 31. — Two cnidoblasts found in a teased preparation of the ectoderm of 

 a fresh tentacle. 



Fig. 32. — Two unexploded nematocysts found in the same preparation. 



Fig. 33. — A section cut very obliquely through a ccelenteron of a polyp 

 some distance below the surface of the colony. In the upper portion the pro- 

 toplasmic portion of the myo-epithelial cells are cut across; in the lower 

 portion, marked by an asterisk, the circular arrangement of the muscular fibres 

 of these cells may be seen. Outside the limits of the tube the mesogloea may 

 be seen with its strings and clumps of cells, stellate cells and fibres. 



Fig. 34. — The appearance of the protoplasmic portion of the myo-epithelium 

 as seen in such a section as that figured in 33, showing the large, irregular, 

 intercellular spaces. 



Fig. 35. — The circular muscle-fibres of the endoderm lining the ccelenteron, 

 such as are represented at the point marked with an asterisk in Fig. 33, but 

 more highly magnified, showing the endodermic nerve plexus. 



Fig. 36. — A string of cells from the mesogloea (osmic acid preparation) 

 showing intra-cellular bodies (_^r.) of doubtful meaning, but possibly parasitic 

 sporozoa. 



Fig. 37. — Transverse section through a mesentery in March, showing a young 

 ovary {gon. ? ). Some of the young ova have a single nucleus containing a 

 few chromatin granules in it ; others have a single nucleus which stains deeply 

 and is homogeneous ; others again liave two nuclei, one of each kind. 



Fig. 38. — Transverse section taken through a mesentery later in the year, 

 showing an older ovary. One of the ova (o?^'.) has reached a considerable 

 size ; another (ow".) contains two ova partly disentegrated. 



Fig. 39. — Section through an ovum in the month of September, x 125 dia- 

 meters, showing the nucleus {g.v^ containing a single large nucleolus situated 

 at a short distance from the periphery. 



Fig. 40. — Section through an ovum in the month of December, x 125 dia- 

 meters. The nucleus {g. ».) contains a number of chromatin granules, but no 

 large nucleolus. It is situated quite at the periphery. 



Fig. 41. — Section through a portion of an ovum in December after treat- 

 ment with alcohol, more highly magnified, showing the spaces occupied by 

 the yolk. 



