212 WINTERTON C. CURTIS. 



pearing reproductive organs. Specimens are found in all stages 

 intermediate between Fig. 14 and those which like Fig. 16 have 

 a much smaller number of segments. It thus seems clear that 

 such a specimen as is shown by Fig. 16, a, b, is to be regarded 

 as derived from the " young adult condition " of Fig. 14 by the 

 progressive loss of ripe proglottids and the advance anteriorly of 

 the differentiating reproductive organs. In the specimen just 

 cited (Fig. 16, a, b} there is a total of only 96 proglottids in the 

 chain and the terminal ones are ready to be set free. The repro- 

 ductive organs which in the whole mount are recognizable in the 

 26th proglottid have advanced beyond the point (3Oth) which we 

 have fixed as the very minimum for the number of " anterior 

 proglottids." There is as yet no sign of the appearance of new 

 proglottids to make good those which have been shed. We 

 might refer to this as an adult which is approaching the old age 

 period of the strobilla in contrast to such a "young adult" as 

 Fig. 14 shows. 



Specimens with a smaller number of proglottids and showing 

 the posterior ones well matured have been frequently observed, 

 but when the number has been reduced much beyond this point 

 (Fig. 1 6) one finds an important change occurring in the region 

 between the first of the old " anterior proglottids " and the sco- 

 lex. This change consists in the growth of this region into what 

 I shall call a " neck " which soon separates the scolex and the 

 first proglottid by a very appreciable distance (Fig. 21, PI. VII.). 

 In this figure the reproductive organs are recognizable in the i/th 

 proglottid and probably occurred further forward but the speci- 

 men from which this was drawn was poorly stained for this point. 

 Such a specimen as Fig. 15, PI. VI., shows the reproductive 

 organs well established in the 5th segment while in the loth and 

 last one they are fully matured. Such a case as Fig. 18, PI. VI., 

 has clearly come from an old chain which has formed a " neck ' 

 to which two of the old anterior proglottids are attached. It is 

 very possible, however, that this specimen which I found among 

 many other preserved specimens has had some segments detached 

 in the collection or subsequent handling. 



Specimens in which the neck has become well established next 

 show a segmentation at the posterior end of the neck region (Fig. 



