300 PROCEEDINGS OF THE ACADEMY OF [May, 



also to the fact that they sometimes curl at the eud wheu cut, and 

 are therefore elastic. I have seen both of these effects, and would 

 add merely that I have seen them in the intercellular fibres and 

 those of the typhlosole more commonly than elsewhere. 



Ide regarded the fibres as mere thickenings of the cytoplasmic 

 reticulum, a view in perfect consistency Avith the reticular theory to 

 which he holds. INIcMurrich does not agree that they are mere 

 thickenings, and insists that they are entirely independent of the 

 reticulum. MclNIurrich is quite right in aflirmiug this indepen- 

 dence, as many of my figures will show ; nevertheless, it is true, as he 

 discerns, that the fibres are cytoplasmic products. The only excep- 

 tion I would take to his view is with reference to their origin. He 

 states that " in very young specimens of Porcellio and Arma- 

 dillidium no trace of the fibres is to be discovered ; and in a speci- 

 men of Oniscus measuring only 4 mm. in length they are but 

 slightly developed, projecting into the cytoplasm from the basement 

 membrane [from which they develop] but a short distance." Un- 

 fortunately McMurrich does not state how large his " very young 

 specimens ' ' were. In the youngest specimens of Porcellio which I 

 have sectioned (less than 1.8 mm. in length) the fibres are already 

 very evident, although as is to be expected not so strongly developed 

 as in the larger specimens (figs. 2 and 3). I have also sectioned the 

 intestine of an Oniscus meaanring only 1.8 mm., and find the fibres 

 stretching all the ivay through the cell. I cannot say how eai-ly the 

 fibres ai'ise, for these were the youngest individuals to be had in the 

 fall of the year. Unquestionably McMurrich saw fibres which were 

 cut obliquely and which appeared not to extend all the way through 

 the cell. The figure to which he refers is evidently from a moulting 

 animal (see fig. 8, page 309). There does not appear to be very 

 good reason for inferring the origin of the fibres from the basement 

 membrane merely because they can be traced to the membrane. 

 My figs. 11, -B, and 12 exhibit complete continuity between base- 

 ment membrane and fibres. A safer conclusion from the facts 

 would be that the fibres and membrane are both formed by the 

 cytoplasm and may be formed in continuity. This would account 

 for the appearance of a cell memoraue in fig. 12. 



a. Cytoplmm. 

 The earliest observers saw in these cells the fibrillar structure of the 

 cytoplasm only. Leydig (17) states that what he described in former 



