676 SCIENTIFIC RECORD FOR 1882. 



VI. WORMS. 



ORTHONECTIDS. 



Julin (Charles). Contribution 5, I'histoire des M^sozoaires. Recherches sur I'organ- 

 isation et le d6veloppement embryonnaire des Ortbonectides. Avec 3 pi. Arch, de 

 Biolog., t. Ill, pp. 1-54. 



DICYEMIDS. 



Van Benedeu (Edouard). Contribution h I'histoire des Dicyemides. Avec 2 pi. Arch. 



de Biolog., t. 3, pp. 195-228. 

 Whitman (C. 0.). A contribution to the embryology, life-history, and classification 



of the Dicyemids. With 5 plates. MitiheU. Zoolog. Station eu Neapel, iv bd, pp. 



1-89. 



Characteristics of the Dicyemids. 



The peculiar parasites known as Dicyemids, found in the renal organs 

 of the Dibranchiate Cephalopods, have been the subject of an elaborate 

 monograph by Dr. O. 0. Whitman, and much light has been thrown on 

 their true nature. 



The Dicyemids are of special interest, inasm.uch as Professor Van Bene- 

 den regarded them as the constituents of a i)rimary group of animals in- 

 termediate between the Protozoans and Metazoans (all animals above 

 Protozoans), distinguished as many-celled animals, developing only two 

 germ-layers, and destitute of a mesoderm. Dr. Whitman's studies, how- 

 ever, have led him to consider that the " Dicyemids may be said to have 

 a transient triploblastic stage, represented by an ectodermal layer, an 

 axial endodermic cell, and two intermediate mesodermic cells, derived 

 from the two poles of the endodermic cell." 



Prof. Edouard Yan Beueden was led to believe that there was an 

 extraordinary parallelism as to mutual relations between the Dicyemids 

 and their hosts, and that they were differentiated in ratio to the ceph- 

 alopods — genus for genus and species for species ; thus, two species of 

 Dicyema accompanied two species of Octopus, two of Bioyemella two of 

 Eledone, two of Dicyemina two of Sepia, and one of Dicyemopsis one of 

 Sepiola. Dr. WTiitman, on the contrary, failed to confirm the generic sub- 

 divisions of Van Beneden and discovered that the species of Dicyemids 

 were not limited respectively to single species of cephalopods, or the 

 sole parasites of their kind on their respective hosts. The American 

 naturalist was led to differentiate all the known Dicyemids into two 

 genera; Dicyema with one eight-celled "head" or calotte, including 

 seven species, and Bicyemennea, with a nine-celled calotte, formed for 

 three other species. In two species of Decaceres of different families 

 were found two species of Dicyemids of the two genera (but different 

 sets of species), and the same species of Dicyemids were found in two 

 or three species of cuttle fishes. 



PLATYHELMINTHES. 



Francotte (P.). Sur Fappareil escr6teur des Turbellairds Rbabdocoeles et Dendro- 

 coeles. Avec 1 pi. Bull. Acad. Sc.,Belg. (3), t. in, pp. 88-98. 



