343 E. RAY LANKESTER. 



ture in so small an organism, but at the same time it would 

 not be surprising were the vascular system absent in some 

 genera and species of the class, though present in their allies. 

 The Annelids afford a parallel. 



Remarks on the Structure of the Gregarinje, and on the 

 Development of G. {Monocijstis) Sipunculi, Koll. 

 By E. Ray Lankester, M.A. (With Plate XX.) 



The Sti'iaiion of the Tunics of Gregarmida. — Whilst the 

 term Gregarines has been in everybody's mouth in relation 

 to a parasitic growth on hair — which could only have been 

 ascribed to these organisms as a result of profound igno- 

 rance — there has been on the other hand considerable 

 advance in our knowledge of the life-history and strvicture 

 of those Protozoa to which the name Gregarina rightly 

 belongs, in consequence of the admirable investigation by 

 Professor Edouard van Beneden of the Gregarina parasite in 

 the small intestine of the lobster. 



The researches have been published in full m this Journal, 

 and therefore in offering a fcAV criticisms on Prof, van 

 Beneden's most recent conclusions with respect to the struc- 

 ture of GregarinsB, we may fairly suppose the reader to be 

 acquainted already Avith that author's views. 



In G. gigantea Prof, van Beneden recognises an outer 

 cuticle, beneath this a muscular layer consisting of delicate 

 hoops arranged horizontally at intervals in a homogeneous 

 matrix ; within this again a more or less pellucid cortical 

 substance, and finally, the axial or medullary mobile granu- 

 lar "contents" with the nucleus. Van Beneden docs not 

 susrgest that all these differentiations of the substance of the 

 organism are to be found in all Gregarinida ; and in this he 

 is quite wise. I do not hesitate to state that in many 

 Gregarinida there is nothing corresponding to his trans- 

 versely striated or muscular layer, whilst in many, and in 

 the younger condition of all, the cuticle is of so delicate a 

 nature, if it exist at all, as not to be recognisable; e.g. 

 Monocystis nereidis (pellucida, Koll.), and the smaller forms 

 of 31. lunibrlci. Being greatly interested in Van Beneden's 

 discovery of the coat of " circular fibrils" in the Gregarina 

 of the lobster, I have taken an opportunity of examining 

 specimens during this summer, and (using Hartnack's No. 



tccted two ciliated ' lags' near the head, but has not reobserved them in the 

 present batch of Pedalion, 



