12 Art. 3.— T. Kaliuraki : 



and others, the rhabdites are, I believe, of use to the worm in 

 securing food as well as for offensive and defensive purposes. 



Basement Membrane. 



Immediately inwards to the epidermis comes the basement 

 membrane which is in most place a well marked laj^er, and varies 

 in thickness according to individuals and to parts of an individual. 

 Generally the membrane is somewhat thicker on the dorsal side 

 than on the ventral and grows thinner as it passes over to the 

 ventral side. Its thickness cannot be measured with any accuracy, 

 the extremes, liowever, l)eing 1 ,« and 4 /^. It seems to be some- 

 what thicker in Uct. linmiU than in other two forms, of which I 

 have treated. Judging from the varying reaction to stains the 

 membrane is apparent^ diiïerentiated microchemically from both 

 the parenchyma and the epidermis. In carmine or haematoxylin 

 preparations it is always much more stainable than the epidermis 

 and the parenchyma, and is distinctly marked off from both. 

 The membrane appears in vertical sections nearly homogeneous, 

 showing no granular feature, but it apparently presents in horizon- 

 tal sections a fibrillated appearance. The course of the fibrillae, 

 though more or less irregular, is, on the whole, parallel to the 

 body surface and thus at right angles to the fibrillae of the 

 epidermal cells. Externally the basement membrane presents a 

 fine scalloped appearance, which may probably be due to the in- 

 sertion of the epidermis; internally it is less sharply differentiated 

 from the parenchyma, and fine striations, forming a loose mesh- 

 work, run out of the membrane to the latter. 



WooDw^ORTii (74) Ijelieves the basement membrane of PJiago- 

 cata gracilis to be a hypodermal product. However, my own 

 observations of the fibrillous nature of the membrane seem to 

 render more evident its probable continuit}- with the parenchyma. 

 Genetically therefore it belongs to the parenchyma» rather tliaii to 

 -the epidermis, as mentioned by several authors. 



