274 Annals Entomological Society of America [Vol. XV, 



Fig. 6. Cross section at level No. 6, showing the Malpighian tubules forming 

 in the hind intestine; also the breaking up of the ectal circular muscles. 

 Note the presence of intima which indicates the structure as being a 

 part of the hind intestine. 



Fig. 7. A cross section slightly cephalad of the level of Fig. 6, showing the 

 digestive epithelium in diagram and the heavy layer of longitudinal 

 muscles characteristic of the mesenteron. The ventral pair of 

 Malpighian tubules are seen here just coming to the surface. 



Fig. 8. A portion of a cross section of the mesenteron of Limnophilus indivisus,. 

 which shows the normal two rows of muscles. 



Plate XVII. 

 Blood Gills of Hydropsychodes analis. 



Cross section of anal region to show the T-shaped anus. X 70. 



Cross section through the anus with a gill lying in the aperture. X 70. 



Cross section through the rectum showing all four gills. X 70. 



Cross section through the "so-called rectal valve." X 140. 



Sagittal section of the gill region showing the intestinal wall invagina- 

 tions that make the valve as at Fig. 4, and later make the gill wall 

 itself and are continuous with the rectal wall caudad of the gills. 



vSagittal section of the gill region to show the retractile muscle of the 

 gill and the relation to the body wall. 



Sagittal section of the gill region with the blood gills extended in 

 function. X 125. 



Cross section of a functioning gill showing the three muscle branches. 



The blood which fills the gills when in function. X 320. 



Plate XVIII. 

 Dorsal view of the silk glands and Gilson"s gland of L. indivisiis. 

 Ventral view of the mouth parts of L. indivisiis with the silk glands 



located. 

 Lateral aspect of the mouth parts of L. indivisiis. 

 Dorsal aspect of the silk glands in relation to the suboe.sophageal 



ganglion. 

 Lateral aspect of a portion of the silk gland. 

 Cross section of the gland proper of the silk gland of H. analis. 

 Cross section of the gland proper of the silk gland of L. indivisiis. 

 Longitudinal section of a Malpighian tubule. 

 Cross section of a Malpighian tubule. 

 Dorsal aspect of the Gilson's gland of P. internipta in relation to the 



prothoracic ganglion. 

 Dorsal aspect of the Gilson's gland of L. indivisiis in relation to the 



prothoracic ganglion. 

 Ventral aspect of the glands in the labial sclerite of L. indivisiis. X 120. 

 Ventral aspect of the gland in a maxillary sclerite of L. indivisiis. X 120. 

 Ventral aspect of the maxillary gland of Henseval and Lucas. X 30. 

 Ventral aspect of the mandibular gland. X 30. 

 Cross section of several of the unicellular portions of the maxillary gland 



of Henseval and Lucas. X 30. 



