31] LIFE HISTOR Y OF TREMA TODES—FA UST 31 



the myoblasts are oval (Figs. 118, 119), The cells very early send out 

 long protoplasmic strands along well defined paths. While the processes 

 from the myoblasts may emerge from any part of the cell, the longitudinal 

 strands are always directed in a longitudinal plane, and the circular fibers 

 are always circular. A unique picture is presented at the point where the 

 furcae of the digestive tract arise (Fig. 118). Here there are two anterior 

 processes running cephalad, and three strands proceeding caudad along each 

 cecum. The chromatin in the nucleus of the myoblast is usually confined 

 to the karyosome. 



ARMATURE OF THE TREMATODE 



The miracidium and sporocysts are not ordinarily provided with hooks 

 or any piercing armature. The redia is usually conspicuous because of its oral 

 sucker, pharynx and gut, and not because of any armature. In the cercaria, 

 however, are found, even in some of the most delicate species, spines covering 

 the basement membrane, especially in the region of the head. In the special 

 group of the stylet cercariae the stylet is the larval organ which is of specific 

 systematic value. 



It is not a universal rule, however, that all rediae and sporocysts are un- 

 armed. At times a modification of the posterior wall of the redia is produced 

 as in the redia of C. biflexa, where the terminal organ is spinose (Fig. 141). 

 Leiper and Atkinson (1915:202) found the second sporocyst generation of 

 Schistosoma japonicum to be covered with a spinous integument. JMore 

 conspicuous is the prepharynx organ of the redia of Cercaria pellucida (Fig. 7). 

 This organ is four-lobed, and has on the outer side of each lobe long spines 

 projecting forward and small spines directed laterad. The use of such a 

 weapon within the soft parts of the host tissue produces untold injury. 



No armature has been observed on the body of any monostome cercaria. 

 The holostome, Tetracotyle pipientis (Fig. 47), has a spinose covering over the 

 entire body and special spines in the region of the acetabulum and accessory 

 suctorial grooves. Spinose modifications are common in the distome group, 

 and in some cercariae, setiferous modifications of the tail. The t^-pes which 

 the writer has examined have the armature confined to the body. They will 

 be discussed under the headings of 1) general body spines, 2) spines of the 

 oral aperture, 3) collar spines of the echinostomes, and 4) the stylet organ 

 of the xiphidiocercariae. In addition there are the spines at the posterior 

 end of the trunk in the caudal pockets. Their probable locomotor function 

 has made it necessary to consider them in another place. 



In many cercariae there is a tendency for the entire bodily integument 

 to become modified so that the surface bristles with needle-like spines. These 

 are usually arranged in a regular diamond pattern, and are more fully devel- 

 oped at the anterior end of the body than in the caudal portion (Figure 90). 

 This condition is found in some xiphidiocercariae and some echinostomes. 

 The spines are always pointed forward. They are more fully developed in 

 the anterior region of the body. 



