MUSEUM OF COMPARATIVE ZOOLOGY. 37 



special " to support the vitality of the male elements, and possibly to 

 aid in fecundation. He states that in PI. polychroa the cocoon is pro- 

 duced in the uterus, but as regards Dendrocoelum lacteum he agrees 

 with lijima in maintaining that the cocoon is formed in the genital 

 cloaca or atrium. In Phagocata I have found ova as well as spermatozoa 

 in the uterus, and believe that fecundation takes place there. The 

 spermatophores are deposited in the vagina and from there the sperma- 

 tozoa make their way into the uterus. I believe also that a portion of 

 the contents of the cocoon are secreted by the uterus, but that the 

 substance of its wall, the shell, is produced from the glandular lining of 

 the vagina, so that in Phagocata at least the " uterus " cannot be re- 

 garded as homologous with the shell gland of Cestodes. It is my pur- 

 pose to discuss at length these questions, together with that of the 

 formation of the spermatophore, in a subsequent paper on the embryology 

 of this species. 



No organ comparable with the " muskulosen Driisenorgan " of lijima 

 ('84, p. 422), or the " vesicule (bourse) copulatrice" of Hallez ('79, p. 57, 

 and '87, p. 20), is present. 



Summary. 



Phagocata differs from all known Triclads in possessing, besides a 

 pharnyx which opens into the intestine at the junction of its three 

 main trunks, many additional pharynges which are joined to the two 

 lateral trunks of the intestine. The lateral pharynges are histologically 

 identical w'ith the median one ; they differ from the latter only in size ; 

 the more remote they are from it, the smaller they are. 



The rhabditi or dermal rods lie between the cells of the hypodermio, 

 not in them. They are developed in cells lying in the sub-hypoderraal 

 mesenchyma ; the cells are connected with the hypodermis by fine 

 tubular prolongations. The connection of the parent cells of the 

 rhabditi with the exterior is a primitive one, and the rods enter the 

 hypodermis by emergence along these prolongations. The rhabditi are 

 ultimately discharged from the hypodermis, and new ones are constantly 

 being developed in new parent cells. They are slowly soluble in water, 

 and are used for securing prey and for protection. 



The parent cells of the rhabditi are unicellular glands, and the rods 

 are their condensed secretions. 



The " Stabchenstrassen " of Ehabdocoeles are homologous with the 

 slime glands in Phagocata. 



