On tlie connective ti^sueä and Ijody cavities of the Neinorteiins. 3 



genesis of the meseiicliyiii, than any other author. In Geonemertes 

 he tinds the inner organs imbedded in a tissue, consisting of fibrous 

 elements. 



HuBRECHT (75 a, b, '87) has applied the term "gelatinous tissue", 

 to the connective tissues, and states ('87) that the gelatinous tissue 

 "is not only present in the space between the body wall and the 

 intestine, but also between the individual muscle-bundles, when these 

 are not very closely applied against each other, and outside of these, 

 between the muscles and the integument, as the so-called basement 

 membrane". This tissue, which he compares to the jelly of the 

 Medusae, he finds in three modifications: 1) the basement membrane 

 of the body epithelium; 2) between the muscle bundles, where it 

 shows a peculiar, homogeneous appearance, with imbedded nuclei; 

 3) around the intestine, consisting of a homogeneous jelly, evincing a 

 dehcate fibrillation, in which nuclei and fibres occur. Hubrecht has 

 also figured the parenchym cells around the dorsal blood vessel 

 (tab. 10, fig. 8), though he makes no reference to them. 



Salenskt ('84), in a paper on the anatomy and development of 

 Monopora vivipara, describes a true coelom, which he characterises 

 as follows: "Le coelome est réduit, au point de ne former qu'une 

 fente insignifiante, seulement appréciable sur une coupe dans le cas 

 où la lame somatique du péritoine se trouve séparée, par hasard, 

 de la lame splanchnique. ... La lame somatique ou la somatopleure 

 . . . se constitue d'une mince membrane formée par une seule assize 

 de cellules aplaties, adjacentes à la face interne de la couche des 

 muscles longitudinaux. La lame splanchnique notablement plus déve- 

 loppée, sourtout chez les mâles, est représentée par un tissu paren- 

 chymateux tapissant le canal digestif; ce tissu s'étend jusque dans 

 les replis que forme 1' epithelium intestinal." The mesoderm cells 

 arise as multipolar delaminations from the blastoderm; that of the 

 head (Mes. céphalique) develops independently from that of the trunk 

 (Mes. somatique). In the former "Ces modifications (of the structure) 

 consistent dans un épaissement du mésoderme et sa division en une 

 lame splanchnique et une lame somatique, ces deux lames délimitant 

 le coelome. ... Il semble que tout le mésoderme céphalique se 

 transforme exclusivement en un tissu parenchymateux". 



Bürger ('90, '95 b) has given careful histological descriptions of 

 certain of the connective tissue elements, in different Nemertean genera, 

 more especially of those elements composing the neurilemmatic layers 

 of the nervous system, and its intracapsular tissue, the interstitial 



1* 



