AND THE DEVELOPMENT OP THE MYRIAPODA. 129 



forms, the Myriapoda; an inference entirely in accordance with the facts subse- 

 quently ascertained respecting the membranes that invest the embryo at the bursting 

 of the ovum. 



Moreover, the few facts detailed in this paper show that the habits of these crea- 

 tures, although hitherto comparatively neglected, are as interesting to the naturalist 

 as those of the more extensively investigated divisions of other Articulata. 



But it is in the evolution of the embryo that the facts ascertained appear to be of 

 the greatest interest. In conformity with the views of Schwann and Schleiden, and 

 of our own accurate observer, Dr. Martin Barry, the embryo of lulus in its earlier 

 stages is found to be composed entirely of a congeries of cells, thus assimilating in 

 origin the animal to the vegetable creation. But in the higher animals, as is well 

 known, in which, chiefly, this subject has been studied, the changes which the future 

 being undergoes in this stage of its existence are so exceedingly rapid, that it is with 

 great difficulty that the facts connected with them are ascertained. In the embryo 

 of the Myriapoda these changes are more gradual, and the transitions more slowly 

 marked. Besides confirming the statements of Savi and Waga regarding the apodal 

 condition of the embryo at the bursting of its shell, and its hexapodal state at a later 

 period, I have noticed the important additional facts of the detection of the amnion 

 and chorion [?] which inclosed the embryo, and also the insertion of the funis at the 

 posterior margin of the penultimate segment of the body, instead of at the dorsal part 

 of the thoracic region, as seen by Rathke in Crustacea; thus more closely identifying 

 the structures of the embryo, as well as those of the ovum in Myriapoda, with similar 

 structures in the ovum, and its development in the higher classes, and further illus- 

 trating the persistence of one general law or principle in the development of ani- 

 mated beings. 



But not less interesting is the fact, that the growth of the animal takes place by the 

 addition of entirely new segments, developed in the germinal membrane that con- 

 nects the penultimate with the then ante-penultimate segment. This mode of increase 

 by the generation of new segments, and not by the extension or division of those 

 already formed, closely connects the Myriapoda with the Annelides, and somewhat 

 resembles the growth of segments in the fissi parous Naiades of the latter class, as re- 

 marked to me by my friend Dr. Baly, when examining the specimen beneath the 

 microscope. But it differs from the reproduction in these animals, in the circumstance 

 that the segments produced are not the terminal segments of the body, but are new 

 formations in the germinal membrane interposed between the newly formed ante- and 

 the permanent penultimate segment. 



The development of segments is one of the first changes in the embryo, and com- 

 n^ences even before it bursts from the amnion. It is repeated with corresponding 

 numbers at each change of tegument. In the lulus terrestris, during the earlier 

 transformations, the addition is sextuple at each change, a ratio that agrees most curi- 

 ously with the number of segments found in the adult state. But it is not to be in- 



