folsom: mouth-paets of anukida maeitima. 99 



In Anurida, they are visible in Stages 1 and 2 only, as slight thick- 

 enings of the germ baud, which are often ill defined in outline and 

 hardly deserve the name of appendages. In fact, their demonstration 

 is largely a matter of technique. I dissected over thirty germ bands 

 for this purpose, stained them variously, and mounted them temporarily 

 in weak glycerine, without finding more than suggestions of the inter- 

 calary appendages. At this point. Miss Claypole most kindly sent me 

 some preparations which were a little clearer than any I had made. 

 These I imitated by staining with Delaheld's htematoxylin, decolorizing 

 with acid alcohol and mounting without pressure in xylol balsam. If 

 care is taken in decolorizing, a condition may be obtained in which all 

 of the germ band between the antennae and mandibles has lost color 

 excepting a rather vague patch on either side, usually not as distinct as 

 in Plate 2, Figure 8% apj). j^r'md. These patches are so slightly, if at 

 all, elevated that they are not distinguishable with certainty in transverse 

 or sagittal sections of the germ band. In good preparations, the lateral 

 boundary of either appendage is indicated by a curving row of ectoder- 

 mal nuclei, and this resemblance to the other paired fundaments is 

 further shown in the presence of an imperfectly developed core of meso- 

 dermal nuclei (Figure 8^, ms'drm.). 



Wheeler and Claypole have represented the appendages much smaller 

 than I have, and appear to have figured the mesodermal core only. In 

 none of Miss Claypole's slides are the appendages outlined as sharply as 

 in the preparation from which my Figure 8"* was made. In glycerine 

 the yolk granules interfere with proper observation, but in balsam this 

 disadvantage is removed. 



Although the appendages are extremely rudimentary, the evidence 

 they furnish of the presence of an intercalary segment is reinforced by 

 the condition of the nervous system, for there is at Stage 5 a small 

 neuromere (Plate 4, Figure 28, tri'ceh.), which, from its relation to the 

 remaining cephalic neuromeres, must be regarded as belonging to the 

 premandibular segment. It ultimately fuses with the deutocerebrum to 

 form a part of the supraoesophageal ganglion. 



Yiallanes first called attention to the tritocerebral segment of insects 

 and Crustacea ; he was afterwards supported by Wheeler, who found 

 that it bore a pair of appendages in Anurida; thus Wheeler ('93, p. 57, 

 Figure VI.) discovered the intercalarj' appendages in this species, and 

 indicated their obscurity by representing them by broken circles. 

 Claypole ('98, p. 263, Plate XXIIL, Figures 40, 47) also observed 

 the appendages, but erroneously inferred that they became modified 



