416 MK. F. E. BEDDAED ON 



however, studied these bodies by the section method, which has 

 allowed ine to describe a good many facts concerning their 

 structure, though something remains to be discovered, as will 

 in due course be pointed out. The wall of the spermatophore 

 is the fii'st part of the structure which calls for attention. This 

 is of some thickness, as is shown in the accompanying figure (text- 

 fig. 135) ; but it is not thicker than that of other spermatophores. 

 Its structure, however, is remai-kable, and in some respects 

 unique, at any rate at first sight. The minute structure of the 



Text-fio-. 135. 



Longitudinal section through spcvmatophore of Fheretlnia moutuua. 



S. Spermatozoa massed at apical end of case. 

 31. Mucous and granular substance filling up blind end of case. 



wall is illustrated in the accompanying figure (text-fig. 136), 

 At first sight, the wall of the spermatophoi-e suggests a living 

 tissue allied to connective tissue or even muscle. We recognise 

 many nuclei, which occur outside, inside, or within the wall itself. 

 These nuclei are not in any Avay degenerate structures, and their 

 varying position shows that they are not merely fi'agments ad- 

 herent to a, sticky structureless wall. For they lie within as well as 

 on both sides of it. In addition to these cells there is a structure- 

 less substance which in parts has a fibrillar character. The likeness 

 to muscle is thereby much enhanced. It occui'i'ed to me at first 

 that the wall might be actually an adventitious sheath foi'med 

 by the tissues of the worm's body, and comparable to the sheaths 

 found round foreign bodies when introduced from the outside, or 



