244 



lop the nerve chords. Metamerie portions of the coelom, divided off 

 by mesenchymatic pseudoepithelia, become the gonads; and the lining, 

 i. e. the mesenchym cells, of these sack gonads, produce the genital 

 products. As a rule, the cytoplasm of these mesenchym cells stains 

 very faintly, and presents a minute alveolar structure. But many of 

 those cells forming the outer (but apparently never the inner) coelo- 

 mic pseudoepithelium, are increased as much as ten times their usual 

 size, and their cytoplasm is filled with deeply staining, nutritive (?) 

 particles, which are also taken into the nucleus, causing a correspond- 

 ing increase in the size of the latter. Since such enlarged cells fre- 

 quently show amitotic stages of division, and are more or less filled 

 with the deeply staining particles, which are also present in the free 

 coelomic cells, I consider the latter to be derived by amitotic division 

 from the former. The mesenchymatic elements of Rhodope (Böhmig, 

 1893) are practically identical with those of C. lacteus. 



The endothelial cells lining the inner surface of the blood-vessels, 

 together with the blood-corpuscles, which Bürger (1. c.) has shown 

 to be derived from them ; and perhaps also the rhynchocoelomic endo- 

 thelium, and the free cells of this cavity; these elements are so simi- 

 lar to the free coelomic cells, that I would consider them also mesen- 

 chymatic in origin. 



IV. The intracapsular connective tissue of the central nervous 

 system. This consists of membraneless, hi- or multipolar, branched 

 cells, with a comparatively large nucleus ; the latter is irregular in 

 outline, with a distinct chromatic net -work, lying in the achromatic 

 nuclear sap. The fine fibres of these cells, envelop the ganglion-cells, 

 and to some extent, form the nerve-sheaths. Three modifications of 

 these cells occur: 



a) Cells between the outer and inner neurilemma, in the brain 

 lobes. Characterized by a finely-granular pigment. 



b) Cells 'between the outer and inner neurilemma, in the lateral 

 chords. Similar to a), but contain no pigment. 



c) Cells in the brain lobes and lateral chords, around and in the 

 fibrous core. Similar to b), but with a smaller, more deeply staining, 

 nucleus. 



I was unable to find the interstitial connective tissue of the body 

 epithelium, mentioned by Co e (1. c.) 



In the immature specimen of C. lacteus studied, a well-marked 

 coelom is present, which is lined (though not continuously) with a 

 layer of mesenchymatic cells, which is also transversed by such cells, 

 and in the fluid of which free mesenchym cells are found. Though 

 not as extensive as the coelom of the annelids, it is nevertheless com- 



