74 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



enters iii^ou an intraoelhilar existence, penetrating into the interior 

 of the red bkjod and other t-ells of the host, wliere, protected by the 

 cell membrane, it grows l^y feeding on tlie cell contents. Finally, 

 its conliiined growth ])r(Kln('es distension, and nltimatcly rupture of 

 the cell-iueinbrane, and the myxosporidium becoiues free. It now 

 moves about amoeboidly, grows larger, the nuclei become more num- 

 erous through karyokinesis, and spore formation begins. This last 

 process is not confined to the last stages of the life cycle, but begins 

 early and is progressive. 



At this period the myxosporidium exhibits the following structnie: 



In outline it is vermiform, sacculated, roundish or not infrequently 

 entirely irregular (see pis. 29, 37-30, 43-45). It usually possesses the 

 power of amceboid movement and generally exhibits a distinct separa- 

 tion of ectoplasm and endoplasm (see pi. 39, figs. 1, 2, and pi. 44, fig. 1). 



The (M'to])lasm (see pi. 10, fig. 4; pi. 39, fig. 1; and pi. 44, fig, 3) is 

 very transi>arent, quite or nearly destitute of grannies, sometimes more 

 or less radiate-striate, and is often prolonged into pseudopodia which 

 only involve the endoplasm wiien of very large size. Tlie pseudopodia 

 sometimes form a shaggy or bristly coat over the Avhole, or a pa it of 

 the myxosporidium (see pi. 44, fig. la). 



The endoi)lasm (see pi. 37, fig. 4; pi. 38, fig. 1, and pi. 39, fig. 1) 

 is more or less coarsely granular and contains nnmerous nuclei, fat- 

 globules, hjTpraatoidin crystals (pi. 44, fig. 5) and other iiigment. The 

 nuclei are derived from the primitive nuclei of the myxosporidium (the 

 nuclei of the sporoplasm; see below). The hannatoidin crystals are 

 usually found within the fat-globules. The myxosporidium may contain 

 other extraneous pigment, e. g., bile-, and perhaps a in^iper, pigment 

 (see pp. 70, 277). 



Spore formation: Each nucleus attracts to it a portion of the sur- 

 rounding myxoplasm to form a pale, solid globule termed the i)ansi)oro- 

 blast (pi. 12, fig. 1 a-c, and pi. 47, fig. 1 «, h) which later segments into a 

 number of sporoblasts (pi. 12, fig. 1 h, i, and pi, 47, fig. 1 e, d)^ each of 

 which develops into a spore. 



2. Spore. — This always contains three elements, shell, capsule with 

 filament, and sporoplasm. The shell (see pi. 10, fig, 3, and pi. 28. fig, 1) 

 is exceedingly transparent, very resistant to chemical reagents, and is 

 frequently bivalve. The capsule (pi. 26, fig. 7, cax).) is a pyriform, 

 hollow, elastic-walled body which always contains a single coiled 

 thread {Jilameitt) capable of extrusion. The sporoplasm (pi. 20, fig. 

 7, spo.) is always a single mass of protoplasm. It contains nuclei (%), 

 and sometimes a vacuole (fig. 7, t-ac), which when present is always 

 single. At maturity the shell splits when bivalve, or dissolves when 

 univalve, thus setting free the sporoplasm (pi. 15, fig. 7 b), which, now 

 become the myxosi)oridium, rebegins the life cycle. 



