432 FAUNA HAWAIIENSIS 



the appearance of a well-marked double line, which is very characteristic, and is well 

 shown in fig. 6. 



Scattered amongst the parenchyma are certain faintly stained cells which seem to 

 be bipolar, and which differ from the cells of the parenchyma both in shape and in their 

 powers of absorbing the staining reagents. These I take to be nerve-cells which are 

 in communication with the nerve-fibres of the lateral cords. The latter are entirely 

 devoid of any nerve-cells on their course. 



Muscle-fibres are scattered through the substance of the body, and one set of 

 longitudinal muscles are most definitely arranged. This layer is situated just below the 

 epidermis in the anterior part of the segment, but as the latter increases in size 

 posteriorly, the cylinder of muscle-fibres, which retains the same diameter throughout, 

 comes to lie more deeply in the tissues. These muscles, like the nervous system and 

 excretory canals, run from segment to segment ; some of them, if not all, end in the 

 cuticle, where it is most bent in at the posterior end of each segment. Laterally the 

 fibres are not in contact, being separated by considerable intervals. Their regular 

 arrangement is shown in fig. 5. 



In the posterior segments, which are so ripe that the slightest touch breaks them 

 off, the parenchyma has undergone considerable degeneration, the cells are less clear, and 

 the spaces of the meshwork are larger and more irregular. 



The generative organs begin to arise very early in the series of segments. Already 

 in the eighth or tenth segment clusters of cells are segregating, and their deep staining 

 shows that they belong to the gonads. In the se.xually ripe segments the ovary is 

 centrally placed, and is supported on each side by a lobe of the testis. From the latter 

 a fine vas deferens leads into an extensive vesicula seminalis, which is as a rule crowded 

 with spermatozoa ; from this a muscular duct leads to the unilateral genital pore. I 

 was unable to make out the details of the penis, and similarly I failed to detect any 

 yolk-gland amongst the female genitalia. 



The vagina leads at once into a large receptaculum seminis, whose walls were 

 strengthened by a series of cuticular-looking rings, whose cut ends are shown in 

 figs. 4 and 6. This communicates both with the oviduct and with the uterus. The 

 latter presents no special points of interest ; in the posterior segments it contains the 

 typical three-hooked larvae, each segment containing at least one hundred and probably 

 more. 



Classification. 



In his paper on taenias in birds, Dr Fuhrmann' remarks that of the 240 odd 

 species of tapeworm described from avian hosts, only twenty-one have been studied 

 anatomically ; the remainder are but little more than names, and probably many of the 

 names are of doubtful validity. 



' Rev. Suisse Zool. tome in. 1895 — 6, p. 433. 



