PROTEOCEPHALUS AMBLOPLITIS LEIDY 181 



SESSIONAL PAPER No. 39b 



mens whose suckers are temporarily evaginated, there is often a sudden invagi- 

 nation of the scolex, while the converse is the case with somewhat older specimens. 

 Both actions are apparently due to the instability of the conditions. 



In young specimens where the scolex is only temporarily protruded, the 

 anterior end bearing the organs of adhesion is somewhat cone-shaped with the 

 base resting squarely on the anterior end of the body proper, as shown in Figs. 

 3 and 4. This structure is also to be seen in the large plerocercoids found in the 

 gonads of the host, but from the size and greater development of the end-organ, 

 which occupies a large space in the apex of the scolex, together with the well- 

 nourished condition of the body, it is obvious that the neck, if the term may be 

 used, is almost obliterated (PI. XIX, Fig. 6). In larvae with the scolices perma- 

 nently extended (PI. XIX, Fig. 5) there is a well-defined neck, while the scolex is 

 shaped like two truncated pyramids placed base to base, thus very closely resem- 

 bling the scolex of the adults of P. ambloplitis as described by Benedict ('00). 

 The body of the worm varies from the oval shape seen in Figs. 1, a, b, and c, PI. XIX, 

 through the elongated oval or elliptical outline of the older invaginated specimens, 

 (PI. XIX, Fig. 2) to the cylindrical form as shown in Figs. 4 and 5, PI. XIX. Later 

 when segmentation commences, the body is quite torulous. The flattening is 

 well marked in those found in the gonads of the host some time before the develop- 

 ment of the rudiments of the male reproductive organs shows that segmentation 

 has commenced. 



After the suckers have become permanently everted they are seen to undergo 

 movements which may be observed at will when the animals are placed in tepid 

 normal saline solution. These movements are rather indefinite and spontaneous 

 at first, but as the plerocercoid develops they become more apparently purposive, 

 and still later they are identical with those observed in adult specimens of P. 

 ambloplitis. When the worm is not attached to the bottom of the receptacle, 

 the suckers grope around here and there through the solution, being alternately 

 protruded and withdrawn in diagonal pairs, while the whole scolex moves slowly 

 to the right or left or occasionally rises from the bottom. The apex does not take 

 part in these movements. Sometimes two adjacent suckers attach themselves 

 firmly to the bottom of the vessel while the two free ones protrude and retract 

 alternately. Again the worm may move along slowly, by alternately freeing and 

 reattaching the two lower suckers while the other two continue with the groping 

 movements. When this takes place the body is drawn along the distance travelled, 

 generally not more than the width of the scolex or the distance between the centres 

 of the adjacent suckers, by a bead-like contraction commencing near the scolex 

 and travelling slowly towards the posterior end of the body. Occasionally all 

 four suckers are used for attachment, and then the only movements to be seen 

 are the contractions which follow one another slowly backwards. After a few 

 seconds of attachment in this manner, the two anterior suckers are raised and the 

 motions are resumed as described above.* 



* A similar movement observed first by Batsch and later by Kraemer for Taenia {Proteoce- 

 •phalus) torulosa Batsch was described as "paarweise. " 



39b— Uh II 



