ON THE DEVELOPMENT OF DERMATOBIA HOMINIS: 493 



hooks of this incomplete circular series number fifteen, of which eight are on the ri^ht 

 side and seven on the left. In the mid-dorsal line two small hooks are intercalated 

 and on the left a single small hook also. 



Somite VI. Here again a row of large hooks marks the anterior margin. At 

 the mid-ventral line is a distinct gap opposite the small hook of the preceding somite 

 and behind this gap stand three hooks of half size, flanked on the right by two single 

 small hooks at some little distance; while on the left two such small hooks are present. 

 In the main row there are five hooks on either side before the beginning of the partial 

 row and from that point seven on the right and eight on the left, making twenty-five 

 hooks in the entire circle. 



Three small hooks on the left represent all there is of a supplementary row on 

 the dorsal side parallel to the main circle and posterior to it. They all stand to the 

 left of the median line. 



The posterior incomplete row begins at the same point as in the two preceding 

 somites. It contains six hooks on the right and seven on the left. In addition to 

 these one hook of half size is located in the series near the mid-dorsal line and sur- 

 rounded by an irregular group of ten small hooks which are scattered in the open 

 space between the series. 



Somite VII. The anterior circle of large hooks is complete except for a small 

 gap in the mid-ventral line corresponding to that of the last somite. There is posterior 

 to this gap a single hook of half size, but no smaller ones on either side in the ventral 

 aspect, while on the dorsal side 'the surface of the body posterior to this series of 

 hooks is entirely devoid of any subsidiary denticles. In this last circle the large hooks 

 number twenty-four, arranged as follows : On the left five from the mid-ventral line 

 to the level of the incomplete series, seven to the mid-dorsal line, six to the end of the 

 incomplete series on the left, and six more from this point to the mid-ventral line. 



Neither an incomplete range of hooks nor a somite furrow indicates the posterior 

 margin of this somite, which merges insensibly into an undivided region without appen- 

 dages or somite limits. This tapers gradually toward the posterior end, where one 

 may distinguish evidence of two somites (PL XXXV, Fig. 5). These may be inter- 

 preted as the tenth and eleventh, according to Brauer ('63). 



Somite X. The anterior margin of this somite (PI. XXXV, Fig. 5) is not dis- 

 tinct, but the general form is that of a collar, 270 micra broad on the ventral surface 

 and 360 micra broad on the dorsal, which is directly continuous with the preceding 

 undivided region of the body. It is covered with fine hooks 33 to 40 micra long and 

 not more than 10 micra broad at the base, being slender and less curved than those 

 of the anterior somites. They are also less heavily chitinized, as is shown by the lighter 



