752 William Patten 



their miclei are represented ; the four armed figures, rt.s. , represent va- 

 riousvìewsof the hyaline, outer ends of the inner circle of retinulae, 1— 7. 



Fig. 77. Is an enlarged drawing of the outer ends of the retinulae 2 — 7; at /, the 

 membrauous sheath is seen projected upon the figure, «.'^— s.*; at//. the 

 tube is beginning to break up iuto its component parts; at /T'. this pro- 

 cess is completed and we see only the seven outer , and isolated ends 

 of the seven pigment cells which help constitute one of the meiubranous 

 tubes (compare rt.s. tig. 79 etc.) ; s.'— ^ represent the outer ends of the 

 inner circle of retinulae, fig. 74 etc. / — 7; «.• — s.^ represents a single (?) 

 piece the outer end of the large median retinula 1. 



Fig. 78. A section through the pigmented collar of four ommatidia. At the corner 

 ///., IV. and V. (representing a section through the inner portion of the 

 collar] only the two cells jj//.' ■M\(ì.p(j.'- have pigment, while only the co- 

 lorless bacilli hc.'^—'' of the other two are seen; at //. the section is sup- 

 posed to pass through the middle of the collar, where both circles of 

 cells are well pigmented. 



Fig. 79. Section of an ommatidium ofPt'??öt'Ms just belo w the collar, showing the 

 pigmented prolongatious of the two inner pigment cells pr/.'-^. Each omma- 

 tidium is surrounded by sixteen of these bacilli , but only four belong to 

 one ommatidium, e. g., 1, -J, 3 and 4. Each bündle of bacilli is surround- 

 ed by a membianous sheath, rt.s. 



Fig. 80. Cross section of the ommatidia (Pt'?me?^.s),towards the inner ends of the rods, 

 showing thetwo sickle-shapedthickeningsof the walls ofthe retinophorae 

 X.; these thickenings are striated, and contain horizontal nerve fibrillae. 



Fig. 81. Cross section of ommatidia [Penaeiis] below the rods. 



Fig. 82 — 88. Represent a series of cross sections taken at intervals from the inner 

 end ofthe calyx fig. 82, to the inner end ofthe style fig. SS, ali the sec- 

 tions are placed in the same direction. 



Fig. 89—92. Represent four successive sections through the swollen ends of the 

 seven retinulae : ali the sections are placed in the same direction, and the 

 cells are numbered lìke those of fig. 74. 



Fig. 93. Cross section through the middle ofthe pedicel, showing the arrangement 

 of the seven retinulae, and the markings of the two Systems of plates. 



Fig. 94. Cross section through the inner end of a pedicel, passing through one 

 of the primary plates; at this end of the pedicel one sees the axial nerve 

 fibre exceptionally well. 



Fig. 95. Still deeper section of the pedicel, passing through a secondary piate, 

 as is shown by the direction of the fibres. The dotted area around the 

 retinulae in figs.95 — 101, is occupied by a circle of cells, fig. 74y., which 

 are completely fiUedwith fat-like crystals, not represented in the drawing. 



Fig. 96 — 100. Represent successive sections through the retinulae surrcmnding the 

 the stalk of the pedicel; one sees that the two pairsof bacilli, befand he-, 

 gradually move from the opposite sides of the ommatidia towards each 

 other , one also sees, with especial clearness, the nerve fibres which sur- 

 round each section of the bacilli. 



Fig. 101. A section of an ommatidium , just above the basai membrane ; the reti- 

 nulae have separated themselves from the stalk of the pedicel , but their 

 general arrangement is the same as before. One sees a few fibres, near ic' 

 and òe.'^, belonging to the outer part of the diagonal bar of the basai 

 membrane. 



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