22 



LUCERNARI^ AND TUEIR ALLIES. 



halves of an oi-an, and conseqncntly, it seems plain enough that the halves of 

 adjoining genitaUa occupy the same umbellar compartment ; or, from another point 

 of view," the halves of the same genitalia are to be found in two different, but 

 juxtaposed compartments of the general cavity. The longest side (>.=) of each 

 triangle faces its mate, and the two have a partition stretching between them 

 equally distant from either. 



51. In a former papcr^ upon this animal we have already drawn attention to 

 the hi'di specialization of these organs when contrasted with those of all the other 

 Acalepha?, and we wish here to emphasize still more strongly the idea which was 

 there set forth for the first time. It has been noticed that these triangular halves 

 are compounded of irregularly roimded bodies so closely set together as to appear 

 like a pavement-work (44). These are nothing less than spherical sacs {figs. 37, 

 61,- 62, ,s), attached one by one, and by a short neck, to the inner face of the 

 floor ; and within these only are to be found the eggs or spermatic material, accord- 

 ing as the animal is male or female. It will be noticed, also, that the largest 

 sacs are in the region of the obtuse angle of each triangle, and that they gradually 

 diminish in size as they approach the basal side (X^) and the distal (>/) and 

 proximal (//) acute angles. Here, again, are two other eminent features of 

 differentiation, and of a degree such as is not equalled in the Avhole class of 

 Acalepha? ; in fact it would seem as if we ought to consider each globular sac as 

 a separate organ, and regard the triangular bodies as merely the expressions of 

 the mode of grouping of the organs. At any rate, the suggestion will serve to 

 heighten the sharpness of the features of differentiation so remarkably worked out 

 here, and may perform the same office in estimating the quality of the same process 

 in other creatures of this class. Nevertheless, we shall at least insist that every 

 organ is composed of two of the triangular groups of spherules, and in this 

 assumption we are supported by other evidence than that already adduced. 



52. The difjitiform bodies (-<), which appear in such large numbers near the base 

 of the proboscis, are arranged with special reference to the divisions of each 

 reproductive organ, and form the connective which gives unity of configuration to 

 the genital halves. They are disposed quite regularly in three or four rows, 

 which lie close together and extend from the proximal end of a partition in a 

 direct line to each of the halves, and then border the shortest side (fig. 22, X") of 

 these triangles for about one-third of their length. We have, then, four groups 

 of digitiform bodies, so appended to the genitalia that they appear not only to 

 hem nr the two parts of each organ, but also to stand as a barrier against 

 communication between any two halves which lie in the same umbellar compart- 

 ment. ^Yc do not pretend to say that they are functionally connected with the 

 genitaUa, but merely describe them thus from a topograpliical point of view. 

 These are extremely flexible, plastic, and muscular bodies, and vary in shape from 

 broad lanceolate, when they are contracted, to linear lanceolate, when extended to 

 their full length. They are very active, constantly in motion, and no doubt serve 



' Lucernaria the Ccenotype of Acalepha;. Troc. Boston Soc. Nat. Hist., March 19, 1862, and 

 American Journ. Science, May, 1803. 



