82 EEPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



Development of the sporohlasts into the spore. — As noted by Biitsclili 

 and Balbiani' in the 2-capsuled fot-ins {Myxoholus), each sporoblast 

 divides into 3 unequal uninucleated masses, 2 small and 1 large, des- 

 tined to form resi^ectively the 2 capsules^ and the sporoplasm. 



a. Development of the capsules. — Very soon there is produced in each 

 of the two smaller masses, ordinarily in the neighborhood of tlie nucleus 

 (see above) a small, rounded, clear vacuole, distinguishable from the 

 surrounding protoplasm by the absence from all points of its wall, of 

 granulation. Next a small protoplasmic button forms at some point of 

 the wall and advances progressively into the vacuole, crowding its con- 

 tents back against the sides, so that after a time it becomes a pyriform 

 body surrounded by a clear layer (the vacuolic contents) and connected 

 with the protoplasm by a pedicle. Little by little the pedicle becomes 

 strangulated, the pyriform body thus finally becoming free. During 

 this time it has acquired a membrane, and a filament is produced within 

 it, evidently at the expense of its protoplasm, although Thelohan was 

 unable to follow all the stages of the process. Around the capsule 

 thus formed one finds the nucleus,^ and debris of the protoplasmic 

 globule which has given birth to the capsule. The nucleus remains 

 most frequently attached to the capsule, but sometimes it becomes 

 separated and is found engulfed in the sporoplasm. During develop- 

 ment the capsules have no fixed direction, orientation taking place later. 



l). Development of the sporoplasm. — The third mass becomes the sporo- 

 plasm. Very early 2 nuclei, generally near together, are seen. They 

 persist to maturity. Thelohan was unable to determine whether these 

 exist primitively in the sporoblasts (which would then contain 4 nuclei 

 instead of 3, as Biitschli sui)poses) or whether they result from 

 division. 



c. Development of the finished spore. — The spores, until now rounded or 

 oblong, very soon assume their definite and characteristic shape and 

 acquire an envelope. The tail is folded against one side of the spore, 

 becoming straight only after the rupture of the pansporoblast mem- 

 brane, which latter persists a rather long time. 



1 Biitschli for M. miilleri; Balbiani for M. elUpsoides (see pp. 218, 223). 



2 Not rarely, especially in Mijxoholus ellipsoides, 3 to 8 capsules are found. The 

 constant association with each of a nucleus shows that their formation takes place 

 in the usual manner. In this case the [pan] sporoblast without doubt incloses an 

 abnormal number of nuclei. Sometimes it even seems probable that a single spore is 

 formed instead of 2 (Th61ohan). [It would be exceedingly interesting to ascertain 

 whether in these cases the number of rejected nuclei is correspondingly less. 

 Unfortunately, at present nothing is known on this point.] 



3 Thelohan here remarks that in a preceding work (Compt. Rend. Acad. Sci. Paris, 

 1889, cix, pp. 920-1, and Annal. de Microgr., 1890, ii, p. 210) he considered these nuclei 

 as belonging to the sporoplasm and attributed to them a dliferent origin, an error 

 which a study of the development has rectified. 



