144 PROCEEDINGS OF THE ACADEMY OF [189i). 



EXPLANATION OF PLATE VII. 



Mesenchytr.eus solifugus. 



Fig. 1. A ventral view of the anterior twelve somites of the worm, 

 showing the position of the spermathecal and male and 

 female genital pores. X 20. st, spermathecal pore at 

 IV-V. d male, 9 female, pores. 



Fig. 2. Profile view of the anterior thirteen somites of the same 

 specimen, showing the jDOsition of the setie bundles. 

 Lettering as before. The lips of the atrium are 

 everted to form a penis. X 20. 



Fig. 3. Semidiagrammatic figure of the reproductive organs con- 

 tained in somites XI-XXII. X about 35. t, testes; 

 ss, left sperm sac; rss, right rudimentary sperm sac; 

 sf, sperm funnel; vd, sperm ducts (the right one, lying 

 within the ovisac, is here represented diagrammatically as 

 nearly straight; the left, lying in the coelom, is exhib- 

 ited with nearly its actual arrangement of folds and 

 coils); se, saccus ejaculatorius; a, atrium; cJ*, male 

 pore, here shown in a position much more laterad than 

 is proper; ov, ovaries; or*, the single ovisac, here 

 represented as only partly filled with ova; 9, female 

 pore in a position more laterad than is natural. 



Fig. 4. Outline of the supraoesophageal gland, from a dissection. 

 X 48. 



Fig, 5. Outline and optical section of a spermatheca showing the 

 three diverticula and the external pore below; the upper 

 end is broken and the ampulla not so large as usual. 

 The point where the break is indicated is about where 

 it becomes continuous with its fellow and opens into the 

 oesophagus. X 48. 



Fig, 6. A section through somite XVI, showing the relation of 

 the sperm sac, ovisac and the sperm ducts to one another 

 and the intestine and nerve cord, x bb. ss, sperm 

 sac filled with developing spermatozoa ; ovs. ovisac con- 

 taining ova and the right sperm duct ; Ivcl, left sperm 

 sac; nc, nerve cord. 



Fig. 7. Median vertical section through the anterior end. X 55. 

 ?«, mouth ; cj), cephalic pore ; eg, supraoesophageal 

 ganghon; nc, ventral nerve cord; ph, pharyngeal pad. 



Fig. 8. Section of a small portion of the body wall, from the pre- 

 clitellar region, showing the remarkable development of 

 pigment granules in the epidermis. X 440. 



