OF OECANTHITS AND TELEAS. 



220 



into the oviduct. The tunica propria of the ovariole is a thin, elastic, structureless 

 and colorless membrane, which in the vitellarium forms a tube whose diameter varies from 

 .06 mm. to 1 mm. 



«f 







. ...f 



Fig- 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. 



Figs. 2, 'i unci 6. Ovarioles of Oecanthus. X125. 2. dissected in sodium chloride solution; 3. from dissection in 0.1 percent, chromic 

 acid; 6. dissected in wa'er. 



Fig. 4. An ovariole of Acheta abbreviate, from a dissection in 0.1 percent, osmic acid. X125. 

 Fig. 5. An ovariole of Acridium sp. from a sodium chloride preparation. X125. 



The germarium 1 is filled more or less completely with cells of characteristic structure 

 which, as sections show, have no definite relations to nor connections with the tunica 

 propria ; but. since there is no trace of an epithelial lining throughout the entire course 

 of the germarium, these cells may in consequence lie in contact with the tunica. 



Since the cells are of nearly the same diameter as the tube in its upper and middle por- 

 tions they are generally disposed in a single row occupying the centre of the tube ; they 



possess egg tubes of the simplest type, where one would 

 naturally seek for the primitive method of egg formation- 

 The results of my observations differ in two essential partic- 

 ulars from the above mentioned theories, viz: in the origin 

 of the egg ami the formation of the yolk. The ovariole 

 in these species varies only in histological details. The 

 four forms represent three sharply defined families of the 

 Orthoptera, and one of them is closely related to the oldest 

 insects in geological time. For an exhaustive treatment of 



the origin of the germ and the formation of the egg, together 

 with a review of the literature and a critical treatment of 

 the theories held at different times on the origin and struc- 

 ture of the insect egg, the reader is referred to Brandt (9)- 

 For a general and comparative account of the origin of the 

 egg throughout the animal kingdom one should consult 

 Ludwig (29) and Balfour (1). 



1 See Bessels's (5) account of the origin and formation of 

 ovarian germs in Lepidoptera, also Miiller (31) ami Clans (12). 



