174 ALBERT C. EYCLESHYMER. 



compared with the successive changes observed in the growth of 

 the normal gills. 



o 



In Ser. I. the first pair of buds formed at about the same rela- 

 tive time as in the normal, but instead of conforming to the rather 

 exceptional pattern of the normal they were symmetrically placed, 

 as shown in Fig. 6. The second pair of filaments while sym- 

 metrical were not present until 96 hours later. In the normal 

 the second pair arose 72 hours after the first pair. The third 

 pair appeared some 48 hours after the second and in both time 

 and place of origin conformed to the normal. The condition 

 about 132 hours later is shown by Fig. 17. Comparing this 

 figure with Fig. 30 it will be noted that but a single filament is 

 present to represent the fourth pair of the normal. Again there 

 are present two intercalated buds while the normal shows none. 



In Ser. II. the filaments appear later than in the normal and 

 instead of arising as a pair there are three buds present (Fig. 6). 

 As the later stages show, the first pair is made up by the tip of 

 the median and the first lateral filament. About 96 hours later, 

 as shown in Fig. 11, three more buds are present. Two of these 

 form a new pair at the base of the gill bar, while the third arises 

 between the tip of the gill bar and the first lateral filament. 

 When compared with the normal of this stage it is obvious at a 

 glance that there is no conformity. No other changes occur 

 which merit detailed description. If the stage shown in Fig. 1 7 

 be compared with that of the normal shown in Fig. 30 it will be 

 readily observed that the regenerated gill is quite unlike the 

 normal, but on the whole it presents a more regular pattern than 

 the normal. 



In Ser. III. the first pair of filaments appeared at about the 

 same relative time as in the normal but at widely separated points, 

 as shown in Fig. 6. The second pair formed some 96 hours 

 later and, alternating with those of the first, gave rise to the pat- 

 tern shown in Fig. 11. The third pair, as shown in Fig. 13, 

 appeared 72 hours after the second as symmetrically placed 

 structures. The fourth pair were likewise symmetrically placed. 



It may be remarked that the remaining five series showed, with 

 slight variations, the same results as described above. In the 



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entire eight series not a single case was observed in which the 



