Studies on maiine Ostracods 75 



and comprehensive arguments than those put forward by G. W. MOller are an absolute necessity. 

 Above all the question as to whether the nervous system may, in spite of its changed condition, 

 possibly afford some information on this subject must be investigated. 



The assumption that the Prot ostracods were characterized by a heart, lateral eyes li'<"-i and eyes. 

 and an unpaired median eye with three parts seems to me very probable. It is now generally 

 considered, as we know, that these organs belonged to the Protostraca. Other writers previous 

 to Gr. W. MUller expressed similar views to his. As early as 1859 E. Grube pointed out, p. 326, 

 that the genera Cypridina and Asterope resembled the Cladocera by their lateral eyes, among 

 other things. C. Claus, in his work of 1865, p. 147, stated that by having a heart and by the 

 development of the organs of sight Cypridina resembled the D a p h n i d s; from his later works 

 it is also clear that he considered these characters as being primitive for the Ostracods. 

 Finally it may be pointed out that F. MOller, 1870, p. 273, assumed that the Protostra- 

 c d s had a heart. In this connection it may also be pointed out that L. LtlDERS, 1909, 

 pp. 117—118, assumes that the genus Gigantocypr is, on account of its well developed system of 

 blood-vessels and its development of blood-corpuscles, is to be considered as more primitive in 

 this respect than other known Ostracods. 



With regard to the assumption that the Protostracods had alimentary organs Alimentary organs. 

 of about the same simple type as those of the recent Cypridinids it seems to me that 

 no serious objection can be raised against it. We may note, however, that W. Giesbrecht, 

 1913, p. 228, states that Protostraca presumably had metamere coeca on the middle part of 

 the intestines ,,jedenfalls gab es coeca an seinem Vorder- und Hinterende". We find hepatic 

 coeca among the Cypridinids (Asterope) and Halocyprids as well as among 

 Cyprids, Nesideids and C y t h e r i d s. 



The number of the limbs: — The assumption that the Protostracods Number of the limbs. 

 were without the limb corresponding to the second maxilla of othev Crvistacea is connected with the 

 assumption made by this writer, and some others, that the recent Ostracods never have this 

 appendage. With regard to this question I only refer here to what has been shown in connection 

 with this subject on p. 20 of this treatise; see also the brush-shaped organ and the penis. 



The question of the nature of the so-called brush-shaped organ is very difficult Brush-shaped organ. 

 to decide. It is perhaps a limb. But in this case which one? 



In the Nesideids and the C y t h e r i d s this organ is always found in the males, 

 never in the females; in these groups we find it most frequently in the neighbourhood of the 

 fifth limb, sometimes a little in front of and sometimes a little behind it, but it is rarely found 

 so far back as between the sixth limbs. Among the Cyprids it has so far been observed 

 only in one genus, Macrocypris. It has also been found in Cytherella. In the two latter genera 

 this organ is also confined to the males; it is not situated, however, at the same place as in iVe*»- 

 deidae and Cytheridae, but near or somewhat behind the seventh limb. Among the Cypri- 

 dinids this organ has been observed by G. W. MCller behind the seventh limb in the 

 female of Cypridina squamosa G. W. MUller. In all other species of this group, as in all the 

 Halocyprids and P o 1 y c o p i d s in which this organ was sought for, even in the 

 forms investigated by me, it was not found. 



