NUCLEUS OR ENDOPLAST. 75 



Spirostomitm, these constrictions of the endoplast are so evenly developed as 

 to impart to it the aspect of a symmetrical moniliform or necklace-like 

 structure, that may be composed, as shown by Stein in the case of Spirosto- 

 mum ambiguum, of no less than twenty-five or thirty ovate or bead-like 

 segments. Although, as hereafter shown, each ovate element of this elongate 

 endoplast becomes ultimately separated and represents the germ or embryo 

 of a new zooid, any distinct separation between them is rarely recognizable 

 during the normal and mature condition of the animalcule, each consecutive 

 fragment being, for the most part, joined closely and intimately to the one 

 next adjacent. In occasional instances, however, it may be observed that 

 certain of these ovate or bead-like constituents are separated for intervals 

 equal to about one-half of their total length, such interval being bridged 

 over by a slender thread-like connecting filament. This special form of 

 endoplastic configuration, occurring as an exception to the evenly monili- 

 form type of the several last-named genera, is found to foreshadow or pre- 

 typify in a very feeble manner the normal and persistent characteristic of 

 certain other species. Special reference is made here to the endoplastic 

 structure demonstrated by Wrzesniowski to obtain in Loxodes rostrum 

 and LoxopJiyllum meleagris. Under ordinary conditions, the endoplastic 

 system appears to be represented in these types by a number of nodular 

 bodies, either ovate or spherical, distributed irregularly throughout the 

 cortical substance. Examining the same with the aid of reagents and the 

 higher powers of the microscope, it was found, however, by this author 

 that all of these endoplastic nodules were united to one another by a 

 slender and transparent connecting filament or, as it may be conveniently 

 denominated, a " funiculus " the distances between each constituent nodule, 

 and consequent length of the connecting thread, in the case of Loxophyllum, 

 often exceeding by many times the length of the nodules. 



One important modification of endoplastic development, as yet unreferred 

 to, is presented by those species in which this special structure actually 

 exhibits the isolated fragmentary or multiple configuration apparently, 

 but not really, existing in the two last-named forms. The endoplast, 

 in this multiple or compound type of organization, is further found to pre- 

 sent as considerable a series of variation as is associated with that of the 

 contractile vesicle in its multiple condition previously described. Thus, in 

 a large series of animalcules, embracing more especially the members of the 

 Hypotrichous family of the Oxytrichidae, this structure is invariably repre- 

 sented by two elongate-ovate endoplasts, the one usually situated a little in 

 advance of, and the other a little posterior to, the centre line or transverse axis 

 of the animalcule's body. In yet a few other forms belonging to this 

 family group, such as the Onychodromus grandis of Stein, there are normally 

 four such endoplastic elements, these, however, not unfrequently being 

 doubled again through the redivision or fission of each component element. 

 From this simple manifestation of the compound endoplastic formula, every 

 phase of gradation is encountered, until at length, and notably in certain 



