E. MARSHALLI. — SUMMARIES 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. 

 Trabecnlte : 



7. The trabecular are thin and iri'egularly cobweb-like 



in appearance. They consist of continuous protoplasm 

 with nuclei, and thus represent threads and fdnis of 

 a syncytial nature. 



8. A pinacocytal covering is not demonstrable on any 



part of the trabecular S3'stem. It is aj'yparently 

 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 archfeocytes — small cells retaining a blastomeric 



character — are found on the trabeculte ; more especially 

 on the outer surface of the chambei's, where they 

 form congeries of various sizes. 



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

 stance in the form of spherules — are usually found 

 quite sparingly on the trabeculse ; but in places they 

 form massive aggregations, derived from certain 

 archoeocyte-congeries by transformation of cells en 

 masse into thesocytes. 



12. The generality of the archfeocyte-congeries is apparently 



concerned in the formation of certain reproductive 

 bodies (?of an asexual nature). 



