OF A SILUROID; S. HIROTA. 377 



apparent absence of nerve-bundles and the presence of pigment cells. 

 The first cu'cumstance is perhaps owing to the difficulty of distinguish- 

 ing nervous from muscular fibres in such a young stage, while the 

 second circumstance is due to the small size of the organ in which the 

 pigment cells have not yet begun to disperse. At all events, the 

 general plan of the structure of the inner zone can be made out in 

 such an early stage. 



The inner zone has already been examined by Brock. The 

 lymph-cavities as well as nerve-bundles seem to have escaped his notice 

 while he considered the veins as the most important part of the organ. 

 He savs : — " Das cranze Orofan wird vom Stiel bis in seine feinsten 

 Verzweigungen von ungeheuer entwickelten Bluträumen entgenom- 

 men, die zum Theil noch mit geronnenem Blute dicht gefüllt sind 

 (Fig. 3 s). Diese Bluträume sind begrenzt von mächtigen Balken 

 (Fig. 3 m), -welche überwiegend in der Längsrichtung der einzelnen 

 Zotten angeordnet sind, so dass die Bluträume polygonale lange- 

 g-ezoofene Maschen bilden, vs'elche unter einander in offener ^^erbin- 

 duno- stehen * * *." These larcre blood-spaces he considers a 

 |)art of the venous system. Then he proceeds to say " dass wir hier 

 ein typische cavernüses Gewebe vor uns haben " and " dass ein Organ 

 in dem wir cavernöses Gewebe in überwiegender Menge vertreten 

 finden auch erektil sein muss." Thus, according to Brock, the whole 

 inside of the organ is, so to speak, nothing but large anastomosing 

 blood spaces and under the circumstance the organ itself must be 

 erectile. From the description which I have given above, it will not 

 be surprising that I find myself unable to accept these statements of 

 Brock's. It is true that in some longitudinal sections through such 

 parts as are given in Fig. 16 where numerous branches of veins and of 

 lymph-cavities are present we often meet with a picture which reminds 

 us of Fig. 3 of Brock's paper, but if we trace the so-called " Bluträume " 



