IO2 \V. M. SMALLWOOD. 



After studying a considerable number of animals in serial sec- 

 tions I find but one type of muscle cell. The contractile tissue 

 is arranged around the outside of the cell and is striated in most 

 instances. Within the contractile region there is a granular 

 protoplasm containing a spherical nucleus which corresponds to 

 the ordinary nucleus found in any tissue. Voigt, '86, describes 

 several arrangements for the contractile tissue in the European 

 form B. varians. 



The nervous system in both B. instabilia and pulcherriuia can 

 be easily seen in a mounted specimen and the ganglionic swell- 

 ings in the latter make a very clear demonstration of their rela- 

 tion to somites. In section the nerve strand is seen to be clearly 

 bilaterally symmetrical. 



My chief observations are concerning the development of the 

 sex cells and the results do not confirm all of the work done by 

 Voigt. Voigt, '85, has given a full description of the formation 

 of the eggs and sperms of the European Branchiobdella varians 

 with 135 figures. The parts of the adult sperm as described by 

 him are the same as those in B. instabilia. Concerning the de- 

 velopment of the germ cells, however, the agreement is not so 

 satisfactory. 



The nebenkorper is unmistakably described for the nucleolus 

 in the ovocyte on page 322. In Fig. 57 " Sind die kerne der 

 spermatocyten noch ungeteilt ; in Zweien von Zellen ist das 

 Nebenkorperchen noch einfach, in den anderen bereits doppelt." 

 In the figure referred to above and in succeeding ones there can 

 be no doubt but that the nucleolus is the body described under 

 the caption of Nebenkorperchen. 



The spermatid has two nebenkorperchen, one that has per- 

 sisted, the other is developed from the thicker protoplasm near 

 the cell wall. " Das eine davon is das Nebenkorperchen, das 

 andere besteht, wie sich herausgestellt hat aus einer Ausamm- 

 lung von dichterem Protoplasma an der Zellwand, da, wo der 

 Schwanzfaden hervorwachst und soil in folgenden als ' Bildungs- 

 korperchen des schvvanzfaden ' bezeichnet werden " (page 324). 



In describing the parts of the adult spermatozoon the neben- 

 kern is derived from the nebenkorperchen, and, as already cited, 

 this latter structure persists and becomes the tip end of the 



