E. MAKSHALLI. — SUMMAEIES OF HISTOLOGY. 191 



6. Around the large apopyle is a narrow membranous 



rim, the marginal membrane, which may be said to 

 be an extension of the connecting membrane over- 

 spreading the interspaces between the apopyles of 

 chambers arranged side by side. 

 Trabecule^ : 



7. The trabeculse are thin and irregularly cobweb-like 



in appearance. They consist of continuous protoplasm 

 with nuclei, and thus represent threads and films of 

 a syncytial nature. 



8. A pinacocytal covering is not demonstrable on any 



part of the trabecular system. It is apparently 

 wanting. 



9. The dermal, the gastral and the canalar membrane, 



as also the membranes mentioned under 6., are 

 adaptations of the general trabecular system. 

 Cellular elements in the trabecular system : 



10. The archœocytes — small cells retaining a blastomeric 



character — are found on the trabecule ; more especially 

 on the outer surface of the chambers, where they 

 form congeries of various sizes. 



11. The thesocytes — cells containing fat-like reserve sub- 

 stance in the form of spherules — ai'e usually found 

 quite sparingly on the trabeculse ; but in places they 

 form massive aggregations, derived from certain 

 archseocyte-congeries by transformation of cells en 

 masse into thesocytes. 



12. The generality of the archœocyte-congeries is apparently 



concerned in the formation of certain reproductive 

 bodies (?of an asexual nature). 



