346 E. RAY LANRESTER. 



nereidis, I did not detect any evidence of circular markings. 

 Neither Van Beneden nor Stuart recognise the existence o± 

 striations in the cuticle in any Gregarinida. 



The true state of the case with regard to the striations 

 visible in the tunic of Gregarinida appears to be this. They 

 may occur in the cuticle (where a cuticle of sufficient distinct- 

 ness exists) , in the cortical substance^ indicative of permanent 

 structural elements (fibrillee), or on the inner surface of the 

 cortical substance^ where it is passing over into the medullary 

 substance, being in this case due to a temporary plication of 

 the cortical substance. 



That the cuticle should be ornamented by striations or 

 other markings is by no means surprising, seeing that they 

 are so usual in the cuticle of Infusoria, and in cuticular struc- 

 tures generally. M. Claparede's description and figure of 

 his Gregarina from Phyllodoce leave no doubt that he refers 

 to a fine longitudinal striation of the surface or cuticle. In 

 describing M. serpula and M. sabella I spoke of the longitu- 

 dinal markings of the surface as simply markings, and did 

 not compare them in any way to the striations of the " inner 

 membrane " or cortical substance, which at the same time 

 were described and drawn. The longitudinal striations in 

 these species are equi-distant, finely ruled markings in the 

 cuticle, comparable to those in the cuticle of Infusoria. As 

 will be seen below, the cuticle of Monocystis sipunculi presents 

 markings of another class, namely, minute tubercles. 



The scattered longitudinal markings of a much less definite 

 and regular character than the foregoing, which are seen at 

 times in the substance of all Gregaringe, and of which I will 

 cite as particular examples, those seen in large specimens of 

 M. /umbilici, those seen by me in M. aphrodita after the 

 action of water, by Leidy in G. blattarum, and by Van 

 Beneden occasionally in his G. gigantea, also apparently 

 those represented in Stuart's figures, but not those described 

 by him, are due to a plication of the cortical substance in 

 consequence of contraction, which throws the inner surface of 

 this dense material into ridges, rendered apparent by the less 

 refractive power of the more fluid medullary substance in 

 contact, or rather in continuity, with which they lie. Such 

 temporary longitudinal ridges may be looked uj)on as the ex- 

 pression of a longitudinal structural arrangement in the 

 cortical substance, but in very few cases that have been 

 observed is there any permanent visible evidence of this 

 structure in the form oi fibriUar elements. 



Such fibrillar elements do, however, occur in some cases, 

 and it seems not impossible that the cortical substance of the 



