^^^^] Alimentary Canal of Altica Larva 



289 



epithehum does not pass out into these projections at all asit 

 does earlier in the instar. At all times, the true cytoplasmic 

 area of the cells is sharply marked off from the fibrillar portion. 

 This fluid doubtless functions in connection with the molting 

 of the -intima of the fore-intestine, for this is of course shed at 

 each molt, with the rest of the chitinous structures derived from 

 the ectoderm. 



The epithehum in the newly hatched larva, and after each of 

 the two molts, lies directly against the intima. This fibrillar 

 secretion is developed in all three of the larval instars. Eventu- 

 ally it also extends out more or less into the undifferentiated 

 hypodermis of the body wall, with which the epithelium is con- 

 tinuous, but this premolting condition is always apparent in the 

 alimentary canal before any of the hypodermal cells are affected 

 In the full grown larva, this area is apparent at least three or 

 tour days before it ceases feeding. The new intima appears on 

 the last day before the larva enters the ground, and the second- 

 ary mtima becomes apparent on the fourth day of prepupal life. 

 The oesophagus is shown in cross-section in figure 4 • a few 

 epithelial cells, in the typical state, in figure 5; a few epitheHal 

 ce s m the premolt condition, in figure G; and a few epitheHal 

 cells after the new intima has been formed, in figure 7. 



Basement membrane. A structureless limiting membrane is 

 clearly distinguishable m all of the sections which were exam- 

 ined. Neither here nor elsewhere in the canal has the writer 

 tound nuclei m the basement membrane, and he believes that 

 it is formed by the hypodermal cells themselves, and is not of 

 connective tissue. 



Longitudinal muscles. From twenty to twenty-five longi- 

 tudinal muscle fibres occur inside of the circular muscle layer 

 1 hey are inserted proximally on the intima at the very begin- 

 ning of the pharynx; they continue not only throughout the 

 fore-intestme, but through the mid-intestine, and a part of the 

 hind-mtestme; distally they are inserted on the intima at the 

 end of the ileum. In a general way, the arrangement of these 

 muscles is like that described by Balbiani (1890) for Cryptops 

 Circular muscles. The circular muscles are strongly' devel- 

 oped. There is but a single layer of them. The most cephalic 

 muscle IS inserted on the intima at the very beginning of the 

 pharynx, but they are lodged in a connective tissue envelope 

 which IS continuous throughout the whole alimentary canal as 



