N o. 2.] THE EM BR VOL OG V OF LIMUL US. 229 



3. The absence of Malpighian tubules, 



4. The absence of salivary glands. 



5. The absence of embryonic envelopes. 



6. The presence of compound eyes. 



II. Limulus and the Arachnids agree in, and both differ 

 from the other ''Tracheatcs" (Hexapoda and Myriapoda) in : — 



7. The primitively postoral condition of appendage I and 

 its later transfer to a prestomial position. 



8. The six-jointed appendages II-V. 



9. The existence of a metastoma (chilaria) upon the sixth 

 somite. 



10. A regional division of the body behind somite VI. 



11. The openings of the genital ducts upon appendage VII. 



12. The subservience of appendages IX to XII (Limulus 

 VIII-XII) to respiration. 



13. The possession of a post-anal spine. 



14. The formation of deutova. 



15. The formation of the entoderm by delamination. 



16. The early appearance of metamerism in the body. 



17. The occasional later appearance of appendage I and its 

 somite. 



18. The existence of a well-marked coelom (schizocoele) ex- 

 tending at first into the appendages. 



19. The extension of the coelom of somite I into the pre- 

 oral region. 



20. The presence of a chitinous entosternite. 



21. The presence of a posterior artery from the heart. 



22. The possession of a pair of sternal arteries passing, one 

 on either side of the oesophagus, to unite below in — 



23. A longitudinal arterial canal upon or surrounding the 

 nervous system. 



24. The possession of blood colored blue by haemocyanin. 



25. In the possession of reticulate genital ducts. 



26. In the method of oviginesis. 



27. In the possession of nephridia in somite V. 



28. In the pitted origin of the nervous system. 



29. In the concentration of the postoral ganglia in a cir- 

 cumoesophageal nerve ring. 



