440 



GEOLOGICAL SUEVEY OF THE TERRITORIES. 



coecal tubes, tlie series of four lower ones being tlie four posterior tubes 

 described by Claus as passing back into the abdomen. In this section 



the dorsal muscles (dm) of the 

 posterior part of the body ap- 

 pear, and the ventral muscles 

 vm) are larger than in section 

 0, while the ovarian tubes (ov) 

 are smaller. 



Without translating in full 

 Clans' description of the heart 

 and circulation we will only give 

 his conclusions. The heart of 

 ^■i^^'P!i^^'pi"H ^ebalia is a long straight tube a 

 W^^iSiMM^iff little thicker just in front of the 

 middle, beginning over the max- 

 illae just in front of the 1st 

 thoracic segment (tergite) and 

 extending to the middle of the 

 4th abdominal segment. It has 

 two pairs of lateral large ostia 

 for the entrance of the venous 

 blood, and four pairs of dorsal 

 arterial openings in the anterior 

 part of the heart. Says Claus : 

 "The heart combines the char- 

 acters of Phyllopods and Mala- 

 riG.67.-Sectionthrouciitbe end of thorax of iVe6aKrt costraca, whilc the tubular dor- 



Upes, showing tho six ccEca (ccec) the heart (ht), the gal VCSSCl passiug thrOUgh twclve 

 ovaries (ov), and the sets of muscles; am, dorsal mus- ^ . . "_ ° , . . 



cles; wn, ventral muscles ; wc, nervous cord ; ot), ovary ; Segments, lU itS lOrm and lU the 



i, intestine. Author del. greater uumber of ostia resem- 



bles the many-chambered dorsal vessel of the Phyllopods, so on the 

 other hand the relation of the two ends with the head and abdominal 

 aortse, together with the hinder jjair of arteries, reminds us of the swift, 

 regular, and in general complicated and vascular circulation of the Mal- 

 acostraca. Of especial interest is the similarity of the shell, or cara- 

 pace-circulation of the Stomapods and Mysidce with Nebalia." 



Of especial interest, says Claus, is the sexual apx)aratus, which com- 

 bines in a snrprising way in structure and form the peculiarities of 

 Phyllopods and Mahi costraca (Amphipoda), and also in position and 

 topograjjhy retains, the primitive relation of the ovaries and testes. 

 Both are slender, long tubes, which lie right and left on the dorsal side 

 of the intestine from the sixth abdominal segment to the region of the 

 stomach (kaumagen), and by means of a short cross passage open out 

 on the thorax. In the male sex this efferent duct opens in the basal 

 segment of the 8th pair of thoracic limbs, namely, in the same j)lace as 

 in the Malacostraca. 



Claus includes Nebalia among the Malacostraca, but when we con- 

 sider the composite nature of the internal organs as described by him, 

 we wonder that he failed to appreciate the independent, synthetic nature 

 of the Phyllocaridan type, which, when we take into account the ex- 

 ternal as well as internal organization, forbids our regarding ISTebalia as 

 a true Malacostracan, though the type of a group standing outside of, 

 but nearer to the Malacostraca than are the Phyllopods. 



The development of Nehalia. — Our knowledge of the development of 

 Nebalia is due to the distinguished Russian embryologist, who in 1868 

 published an elaborate account of the developmental history of Nehalia 



