E. MAESHALLI. — REPKODUCTIVE ELE31ENTS. 187 



Somewhat enigmatic is the process by which are formed the 

 bodies unhesitatingly called by me, because of their structure 

 (p. 162), the larva', in Leitcopsacus orthodocus and VUrollula 

 fertile. As before mentioned, the larvie in both these forms were 

 found in different stages of development. Deferring the details 

 of ray observation on this matter to a further Contribution, it 

 is incumbent on me to mention here that, in a certain early 

 developmental stage, the embryo is spherical in shape and con- 

 sists of a compact mass of small cells, which mass is super- 

 iicially delimited by a layer of cells, whose general apj)earance 

 is like that of the internal cells, but which show an epithelium- 

 like arrangement. There is as yet no flagellation discernible on 

 the external surface, nor are the first spicules developed in the 

 internal cell-mass. The embrj-o occupies a position in the in- 

 current lacunse between the chambers, being apparently devoid 

 of a special follicular envelope. As a still earlier stage, directly 

 preceding the one just mentioned, there is found a simple cellular 

 mass, agreeing in all respects with the latter except in having 

 no distinct epithelial covering. And, that simple cellular mass 

 is in all appearance nothing else than an advanced stage of what 

 I have called the archaeocyte-congeries, of which there exists a 

 series of different sizes, leading down uninterruptedly to the 

 little groups of cells so commonly found on the chambers. At 

 all events, there is nothing else than these compact groups of 

 small cells to which the origin of the develojiing embi'yo can be 

 traced back with any degree of probability. 



brood. That this belonged gencticallv to that very specimen and was not of e.'strinsic 

 origin, is fairly admissible on tlie ground of the very large number of yonng present. 

 The case may be construed as indicative of the fact that the formation of young brocds lakes 

 place in a short period of lime and then in great profusion. The specimen referred to was 

 obtained during the month of Mav. 



