36 JOHN E. GUTBERLET 



They are usually unilateral. The existence of this irregularly 

 alternate occurrence of the genital pores may be an anomaly, but 

 it is rather frequent for such a condition. 



2. Davainea echinobothrida (Megnin 1880) Blanchard 1891 

 Diagnosis : Length up to 250mm ; width 1 to 4 mm. Head 

 (Fig. 22) 0.25 to 0.45 mm. in diameter, with retractile rostellum 

 100 to 150/i in diameter, armed with crown of about 200 hooks 

 arranged in two rows. Suckers round or oval, 90 to 200ju, in diam- 

 eter, armed with 8 to 10 rows of hooks. Rostellar hooks (Fig. 

 23) similar to those of Davainea tctragona, but larger, measuring 

 10 to 13)11 in length. Acetabular hooks (Fig. 24) likewise similar 

 to those of D. teiragona, but also larger; size variable, smallest 

 being 7 or S^u, in length and largest measuring from 14 to 16ju,. 

 Neck thicker and generally shorter than D. tetragona, nearly equal 

 to width of head. Strobila resembling that of D. tetragona, but 

 serrate border more pronounced. Oldest segments in preserved 

 specimens also differ from those of D. tetragona, being less elon- 

 gate and frequently marked by median constriction. Owing to 

 this constriction adjacent borders of most posterior segments pull 

 apart in median line and remain joined only at sides, giving rise 

 to median series of openings through posterior portion of strobila. 

 Genital pores irregularly alternate, or sometimes almost entirely 

 unilateral, situated one in each segment posterior to middle of 

 lateral margin. Male and female canals pass on dorsal side of 

 nerve and excretory vessels. 



Male Reproductive Organs: Testes 20 to 30, arranged in 

 median field surrounding female glands as in D. tetragona. Vas 

 deferens lies in anterior third of segment much as in D. tetragona. 

 Cirrus pouch flask-shaped, 130 to 180ju. in length. Basal portion 

 globular or ovoid, surrounded by layer, about 10;U, thick, of longi- 

 tudinal muscle fibers inside of which is a layer about 12/ji thick 

 of transverse fibers. Neck of pouch measures 50/u, to 75ju, in length 

 by 15 to 20/x in diameter, surrounded by layer of transverse fibers 

 thickened at distal end to form sphincter. According to Megnin, 

 the cirrus is armed with minute spines. 



Female Reproductive Organs'. Female organs same as in 

 Davainea tetragona, and onchospheres (Fig. 25) are also similar 



