224 BULLETIN OF THE BUREAU OP FISHERIES. 



Length of spore 50-6SM, width about 8m; diameter of capsules 4. 5m; length of filament qom. 



Habitat. — Both vegetative and sporulating trophozoites abundant in the gall bladder of Cestracion 

 zygcEna taken July 11, igi4, and in two individuals of Cestracion tiburo taken in July. 



Remarks. — In many respects this species is similar to C. sphcerulosa Thelohan, but the spore is 

 much smaller and the sutural plane is not perpendicular to the longitudinal axis as in sphcF.rulosa accord- 

 ing to Thelohan 's figures. According to Thelohan the spherules in sphccrulosa often contain minute 

 colored granules, but this seems never to be the case in mesospora. This species occurs along with C. 

 recuruata, new species, but can be easily distinguished by the much smaller size of the spherules. 

 Ceratomyza sphairophora, n. sp. (PI. xvii, fig. 17-21, 23; pi. xviii, fig. 22.) 



Trophozoite. — Vegetative trophozoites colorless, transparent, pyriform, elongate. Numerous fine 

 filiform pseudopodia at anterior end. Progressive movements rapid. Ectoplasm clear, homogeneous, 

 forming a distinct layer at anterior end and often a short distance back along the sides. Structure of 

 endoplasm extremely variable, in majority of trophozoites filled with transparent, homogeneous sphe- 

 niles crowded closely together (fig. 17). These spherules never extend to extreme anterior end, the 

 endoplasm in this region being filled with a closely crowded mass of small fat globules. In other cases 

 the spherules are much less distinct (fig. 18) and sometimes, especially in sporulating individuals, the 

 endoplasm may show only a very indistinct vacuolated structure (fig. 22). Usually, however, even 

 sporvilating trophozoites exhibit well-defined spherules. Apparently the indistinctness of the spherules 

 in many cases is due to their becoming less dense until they form more or less distinct polygonal areas 

 separated by a thin layer of granular endoplasm (fig. 18). Another variation is the extreme develop- 

 ment of the spherules. In a small percentage of trophozoites the spherules are much larger than usual, 

 sometimes reaching a diameter of 7-8 n. These large spherules, unlike the smaller, contain numerous 

 minute yellowish or brown granules collected into a mass at the center (fig. 19-20). The spherules or 

 vacuoles, as the case may be, are separated by a thin layer of distinctly granular endoplasm containing 

 numerous rod-shaped or rounded, colorless bodies, which in their appearance are strikingly like small 

 bacteria. That they are, however, not bacteria is shown by the fact that they fail to take the Giemsa 

 stain. Small vegetative trophozoites are usually much like the larger, except that the spherules are 

 not so numerous and there is no distinct mass of fat globules at the anterior end. Occasionally small 

 trophozoites are seen which contain large, clear, irregularly shaped vacuoles varying greatly in size 

 (fig. 21). In the sporulating trophozoites the spores are always situated with the large central portion 

 of the spore at the anterior end, the long attenuated ends of the valves being bent backwards at right 

 angles and extending toward the posterior end of the trophozoite (fig. 22). 



Length of sporulating trophozoites about ioo-iiom width about 25M. 



Disporous. 



Spore. — Valves greatly elongated, tapering gradually toward the ends but abruptly enlarged toward 

 the base (fig. 22, 23). Long, attenuated ends of valves hollow and so fragile that it is almost impossible 

 to find an example in which they are not more or less distorted. As shown in the figures, even after 

 being set free the ends are usually sharply bent toward the postcapsular side a short distance from the 

 sutural plane. Attenuated ends of valves are often twisted or bent in various ways, and there is a marked 

 tendency for the membrane to collapse, especially near the extreme end. Sutural plane perpendicu- 

 lar or only slightly oblique to longitudinal axis. Capsules large, spherical, close together, and slightly 

 convergent, opening some distance apart on the capsular side. Coiled filaments distinct. Sporoplasm 

 confined to large, central part of spores, but extending farther into one valve than the other. 



Total length of spore (i. e., from tip to tip of valves along longitudinal axis) 115-140M, width about 

 I2m; diameter of capsules 6m; length of filament 75M. 



Habitat. — ^Abundant in the gall bladder of the sharp-nosed shark, Scoliodon ierrcB-novcB. 



Remarks. — This species appears to be a remarkably variable one. The assumption that the different 

 types of trophozoites described above belong to one and the same species is based on the fact that simi- 

 lar spores have been seen in all the different types, and that all types of trophozoites with intermediate 

 gradations can be found in the same host. It is remarkable that in the case of C. tasnia, which occurs 

 along with this species, the trophozoites have practically the same structure, even exhibiting the same 

 variations, while the spores are entirely different. 

 Ceratomyxa tsenia, n. sp. (PI. xvii, fig. 24; pi. xviii, fig. 25, 26.) 



Trophozoite. — Vegetative trophozoites similar to those of C. sphairophora, and no character has been 

 found by which they may be distinguished. Spores of this species have been observed in the different 



