REVISION OF STREPSIPTERA PIERCE. 59 



posterior end of the stomach being connected with the outer cover- 

 ings of the last abdominal segment by means of an epithelial band at 

 the point corresponding to the position of the anal opening. Subse- 

 quently this band is apparently resorbed. The anterior intestine 

 becomes flattened from the ventral side to the dorsal and is of uni- 

 form bore. The stomach becomes narrowed, and laterally flattened, 

 and a change of epithelium takes place as in the male (Nassonow, 

 1892 e, pi. 2, fig. 17;' 1892 c, pi. 1, fig. 9). 



Malpighian vessels have not been observed in the larval stage, 

 although rudiments probably corresponding to these vessels were 

 found at the end of the male larval stage. At the anterior end of 

 the intestine of the larva protrudings from the dorsal wall begin to 

 form, three in number, spherical, and situated in one row. (Nassonow, 

 1892 e, pi. 2, figs. 9 e, 14 e.) They are close together and afterwards 

 fuse at their bases and communicate with the cavity of the intestine 

 by one opening, at the same place elongating into blind excrescences 

 (Nassonow, 1892 e, pi. 2, fig. 10 e). These excrescences become larger 

 at the pupal stage, split up, and appear as if anastamosing with one 

 another. Thus the place of the, connection of the excrescences also 

 increases in length and forms a canal by whose means the cavities of 

 the ramification communicate with the cavity of the intestines. This 

 common canal is somewhat expanded at the middle (Nassonow, 1892, 

 pi. 2, figs. 7, 11). 



Nassonow assumes that these formations may correspond to the 

 Malpighian vessels by reason of the mode of origin and location. 



NERVOUS SYSTEM. 



The nervous system in the first days of the parasitic life is very 

 strongly concentrated. The brain, consisting of two large ellipsoid 

 ganglia, extending longitudinally, lies in the first and second thoracic 

 segments. The commissures pass off from the anterior ends of the 

 lobes and extend ventrally to the abdominal mass of ganglia. Optic 

 nerves pass to the ocelli from near the same point. No optic lobes 

 are differentiated. The abdominal mass consists of a fusion of 

 the suboesophageal, thoracic, and abdominal ganglia into one large 

 mass situated in the thoracic and first three abdominal segments 

 (Nassonow, 1892 e, pi. 2, figs. 1, 2, 3, 4). 



As the larva develops the lobes of the brain tend to become trans- 

 verse, the ocular lobes begin to form, and the ocelli gradually disap- 

 pear. The circumcesophageal commissures become more slender while 

 the abdominal ganglion lengthens and becomes constricted at its 

 middle. This constriction becomes greater until the huge ganglion 

 is divided into two smaller ones, the first or "thoracic" lying partly 

 in each of the three thoracic segments, and the second or "ventral" 

 lying in the second and third abdominal segments, and later only in 



