1914] Sharp: Diplodinium ecaudatum 93 



5. Diplodinium ecaudatum forma quadricaudatum forma nova 



PI. 5, fig. 9 



This is again a very abundant form, occurring not only in the 

 majority of cattle but also in great numbers in the individual hosts. 

 In fact this form is almost as abundant as is D. e. forma caudatum. 

 This form is characterized, as its name would indicate, by the pos- 

 session of four spines on the posterior end of the body. This fourth 

 or quaternary spine {sp. 4, pi. 5, fig. 9) occurs normally on the right 

 side of the body about midway between the primary (sp. 1) and ter- 

 tiary {sp. 2) spines. The tertiary spine is then crowded dorsally until 

 it occupies a position somewhat more dorsal than does the secondary 

 spine {sp. 2). In about four per cent of the animals examined the 

 quaternary spine {sp. 4) was located on the left side between the 

 primary {sp. 1) and secondary {sp. 2) spines. "When this is the case 

 the secondar}^ spine {sp. 2) is crowded so far dorsally as to appear to 

 be almost exactlj^ opposite to the ventral or primary spine. On which- 

 ever side it may occur this quaternary spine {sp. 4) is almost invari- 

 ably the smallest and ranges in size from a mere protuberance to a 

 spine almost as large as the secondary spine. In some cases, however, 

 this fourth spine was even larger than either the secondary or tertiary 

 spines. It has been pointed out that in the fixed material the primary 

 spine ordinarily curves dorsally while the secondary and tertiary 

 spines almost invariably curve ventrally and inward. In the case of 

 the quaternary spine this curvature may be either ventrally and in- 

 ward, dorsally and inward, or merely toward the main axis. It is to 

 be noted that the designation of these spines as primary, secondary, 

 etc., has been according to their position rather than to their size. Up 

 to the form under discussion a definite relationship has seemed to exist 

 between size and position, but with D. e. forma quadricaudatum this 

 definite relationship no longer holds, except that the primary spine 

 is always the largest, and the first three spines retain their relative 

 positions. In this connection it is to be noted that considerable varia- 

 tion exists as to the relative lengths of the spines both in relation to 

 each other and in relation to the body. That is to say, each animal 

 may present any one of the three general conditions: (1) all of the 

 spines may be short, (2) all of the spines may be long, or (3) some 

 of the spines may be short and the others long. Cross-sections through 

 the bases of these spines (forma quadricaudatum) show normally a 

 quadrangular arrangement and in many cases the bases of the sec- 



