TAPE-WORMS OF TJII] SUIi-FAMILY AVITKLLININ.K. ;]49 



(5) Near their base the suckers are connected by a system 

 of muscles, Avliich connects the two dorsal suckers with each 

 other and the two ventral suckers with each other, but does 

 not seem to connect the dorsal with the ventral suckers. Its 

 fibres connect : 



(a) The right sides of the two dorsal suckers. 



(b) The left sides of the two dorsal suckers. 



(c) The right sides of the two ventral suckers. 



(d) The left sides of the two ventral suckers. 



The histological elements composing the parenchyma 

 muscles can be divided into the following groups : 



(1) Bipolar myoblasts with terminal fibril la3. 



(2) Bipolar myoblasts with lateral fibrilhe. 



(3) Elongate bipolar myoblasts lying axially within the 

 tubiform muscles of the longitudinal muscles. 



The first group I have only found in the dorso-ventral 

 mnscle ; the second forms the transverse muscle, and occa- 

 sionally occurs in the dorso-ventral muscle; the third occurs 

 in the longitudinal muscle. 



(1) The bipolar myoblasts with terminal fibrilhe 

 occur in all parts of the dorso-ventral muscle, and are its 

 chief components. The cells are spindle-shaped, with an 

 oval nucleus, whose long axis lies in the long axis of the cell 

 (figs. 22, 23). The nucleus measures, on an average, 3'")/.tX 

 4'2o/t; it contains a nucleolus and two or more round chi'O- 

 matin bodies. The plasma stains deeply, and is sharply 

 defined at the margins, as though enclosed by a membrane. 

 At each end of these cells a fibrilla arises, which is several 

 times longer than the cell itself; the fibrilhe are extremely 

 thin, measuring only a fraction of a f.i in diameter, they run 

 in the general direction of the long axis of the cell ; their 

 course is, however, usually not quite straight, but sinuous or 

 zig-zag. The fibrillar may, perhaps, only act as tendons, in 

 which case the cell would represent the contractile portion 

 of the combination, but it is moi-e probable that the fibrilla 

 is itself contractile. These cells are usually found in rows, 

 their fibrillge lying in part apposed to each other, thus form- 



