18 EINAR LÖNNBERG: NOTES ON SPIRULA RETICULATA OV 





they contract they seem able to compress and reduce the volume of the lenticular 

 body with the help of its fibrous capsule. It" the peripheric muscles al< 

 they make the aboral surface less convex, while if the mure central ones which 

 curve centripetally on the oral side of the lenticular body contract they make 

 the aboral surface more convex. Both contractions reduce the volume. the 



outer circumference, away from these muscles we find in tl tions ti 



sally cut bunches of muscles which may be circular. These muscli all 



serve to enable the animal to regulate the compression and dilation of tin- lenti- 

 cular body. The interior of the lenticular body is cellular although, at least in the 

 present condition, the limits of the cellules cannot be discerned, but a vast num- 

 ber of densely crowded nuclei indicate their existence. The nuclei are more nu- 

 merous and lie closer together than in any other tissue. The nuclei are al 

 different and variable in shape and size. We can however discern several different 

 classes. Some nuclei are comparatively small, oval or a little elongate in shape, 

 densely furnished with chromatin and therefore darkly stained, and agree in e. 

 respect with the nuclei of the connective tissue and are without doubt of the -aim- 

 nature. Other nuclei are twice, or more than twice, as large, have less and m 

 dispersed chromatin and for that reason they look pale. The shape of these mich i 

 is often fusiform, sometimes elongate, nearly cylindrical, sometimes shorter and ir- 

 regular. The nuclei of a third class, less numerous than the others, are very nai 

 elongate, often irregular, and rich with chromatin. Sometimes oik- can see a fine- 

 thread (nerve?) in connection with these nuclei. It is evident that the nature and 

 the function of these different nuclei and the cellules to which they belong must be 

 different, but at present this question can hardly be solved. The lenticular body i- 

 richly furnished with bloodvessels and on the sections we find arteries with thick ho- 

 mogeneous walls and an interior endothelium as well as veins and a plexus of capilla- 

 ries of the ordinary structure. The exterior or aboral part of the "terminal papilla" 

 is composed of a connective tissue that looks rather soft. The oval or ellipsoidal 

 lules contain comparatively small oval or roundish nuclei which are rich with chro- 

 matin and very darkly stained. These cellules are imbedded in a richly developed 

 gelatinous matrix, the substance of which is supported by a network of very fine 

 fibrils. Laterally this network becomes stronger and stronger and gradually pa 

 over into the common fibrous connective tissue. On the top of the papilla ther 

 no chromatophores but laterally the interior walls of the "aboral fossa" 11 I'm 



nished with such even to the very base of the papilla. The epithelium on the 

 minal papilla" is destroyed. 



