504 ON THE DEVELOPMENT OF DERMATOBIA HOMINIS 



left. The new skin carries sixteen hooks on the right and twenty on the left. It is 

 noteworthy that in general two new hooks correspond to one old one since one appears 

 beneath the old one and a second in the gap between it and the next. This relation 

 which obtains very generally between the large hooks of this and other rows on the 

 old and new skins respectively is not an absolute one and departures from the rule 

 appear occasionally. An accessory row posterior to this incomplete row and parallel 

 with it contains on the new skin ten to twelve hooks of half size in place of six or eight 

 minute denticles of the old skin. The new hooks are clearly directed cephalad. 



Somite VI. The complete row near the anterior margin bears in the case of the 

 old skin ventrally five hooks on either side and dorso-laterally eight on the left and 

 seven on the right, making twenty-five in all. There is also a single small isolated 

 hook on the mid-ventral line just behind the main row. The left five are replaced 

 on the new skin by nine of about the same size, and the right five by eight, while the 

 single small hook is supplanted by two of half size. Dorso-laterally the right seven 

 are placed by fourteen and the left eight by fifteen, making a total in the row on the 

 new skin of forty-six. On the dorsal side a short series of five hooks of half size appears 

 just behind the complete row as a new formation. On the ventral surface one of half 

 size and two minute denticles posterior to this complete row are succeeded by an almost 

 continuous though slightly irregular row of twenty-five or more hooks of half size 

 posterior and parallel to the main series. The incomplete row on the old skin has 

 eight hooks on the right side and seven on the left, of which the two mid-dorsals are 

 notably smaller than the others. There is also a gap near the mid-dorsal fine and 

 posterior to it a series of a few small denticles. The seven hooks of the left side are 

 succeeded by sixteen and the eight on the right by fourteen of similar size though more 

 variable. The posterior parallel row contains more denticles and much larger 

 ones also on the new skin, while in this row all the new hooks are also directed 

 forward. 



Somite VII. On the outer skin the complete row contains on the right five hooks 

 and on the left six, in both instances ventral to the incomplete series, and seven on 

 each side beyond that point, or twenty-five in all. There is also one small hook near 

 the mid-ventral line and posterior to the row just described. On the new skin the 

 five right hooks are succeeded by nine not so regularly placed nor so uniform in size; 

 the six left are succeeded by nine new hooks, the seven dorso-laterals by eleven variable 

 large hooks on the left and by twelve on the right, making a total for this row on the 

 new skin of forty-one. The largest of the new hooks do not exceed 420 micra in length 

 and their variability is well shown in the camera drawing (Pig. 16). 



The single hook posterior to the row is replaced by an accessory row of eight about 



