PSOROSPERM-SACCULES. 195 



above described rods, contain a perfectly clear protoplasm, or are filled 

 with a uniformly granular substance, in which one can sometimes dis- 

 tinguish a nucleus. 



With these Gregarines are associated, as Leydig 1 first showed, the 

 so-called "Psorosperm-saccules," discovered by J. Mliller. 2 These are 

 parasitic organisms of varying shape, some microscopic, some several 

 millimetres across, found often abundantly in the most diverse situa- 

 tions on the bodies of fishes and frogs (e.g., on the skin, gills, and in the 

 muscles, kidneys, or urinary bladder). To the naked eye, they ap- 

 pear as small white points or sacs. Their close relationship with the 

 Gregarines is proved by the nature of the contents, which consist of 

 hard-shelled Psorospermise, exactly like the Pseudonavicellse. They 

 only differ from the latter in minor characters, as the presence of a 

 tail-like process of the shell, such as is also seen on the eggs of some 

 ectoparasitic Trematodes (p. 45). 



Yet it seems hardly allowable to class these Psorosperm-saccules 3 

 along with the Gregarines. For not only have they no capsular wall, 

 like that surrounding the group of young Pseudonavicellse, but further, 

 the formation of the Psorosperms generally begins at a time when 

 the organisms have not yet attained their full size, and goes on 

 throughout the whole subsequent life. What takes place in the Gre- 

 garines in two successive stages, is in the Psorosperm-saccules distinct 

 neither as regards space nor time. 



And, besides the fact that the formation of Psorosperms takes 

 place without previous encystation, it must also be noted that the 

 resulting organisms have not the nucleus and firm cuticle of the Gre- 

 garines. They appear as simple masses of protoplasm with scattered 

 fatty granules. Their power of motion is also more limited, and is in 

 some cases, especially in the later stages, hardly perceptible. They 

 manifest their activity generally only in protrusion and retraction of 

 a part of their body- substance. 



The formation of Psorosperm-saccules is effected thus the original 

 uniformly granular substance gradually becomes a mass of distinctly 

 defined balls (Fig. 98), which become surrounded with a transparent 

 covering, and then become single or double Psorosperms. These pass 

 away almost as soon as they are formed, and appear in all cases to 

 have a further development, so that their contents have usually a dif- 

 ferent character from that of the ordinary Pseudonavicellse. In some 



1 " Ueber Psorospermien und Gregarinen," Mutter's Archiv f. Anat. u. Physiol., 

 p. 221, 1851. 



2 " Ueber eine eigenthumliche krankhafte parasitische Bildung mit specifisch organ - 

 isirten Samenkbrperchen (Psorospermia)," ibid., p. 477 et seq., 1841. 



3 Our knowledge of the Psorosperm-saccules rests specially on the researches of 

 Lieberkuhn, Mutter's Archiv f. Anat. u. Physiol., pp. 1-24 and 349-368, 1854. 



