T. B. R0SSETER ON DKBPANIDOTAENIA UBDVLATA (KRABBE). 273 



The efferential canal of the ovaries makes a junction with this 

 canal, as also does the yelk and shell glands. The whole of these 

 organs, with the exception of the shell-gland, lie in the central 

 portion of the segment, ventrally, and are so crowded together 

 and superimposed dorsally by the male organs that it is a difficult 

 task to differentiate and study them in sit". 



The paired ovaries (Fig. 5, hh) are composed of follicles whose 

 efferent ducts fuse at the proximal end of each ovary and form 

 the oviduct. The yelk-gland (Fig. 5, j) is dendritic, while the 

 shell-gland (Fig. 5, i) is a long reniform gland which lies posterior 

 to the other organs, and is the only one that can be clearly 

 discriminated. 



The uterus (Fig. 6) is composed of longitudinal pouches. These 

 pouches occupy the whole of the ripe or uterine segment, and 

 they are filled to repletion with oncospheres or six-hooked broods. 

 Usually this hexacanth stage is a spherical object or an elongated 

 homogeneous mass of impregnated protoplasm, waiting to find 

 or be transferred to its specific nurse, so as to be transformed into 

 a cystic scolex — cysticercoid. 



In this instance there is a departure from the usual course of 

 development, w^hich is of itself interesting from an evolutionary 

 standpoint. After passing through a series of successive stages 

 in the uterus (and I have traced it through eight such stages of 

 development), it finally evolves itself into a medusiform body 

 or six-hooked brood (Fig. 9). These six hooks, placed at equal 

 distances, support the velum from the interior of the invaginated 

 gastrula cavity. This medusiform embryo is enveloped by two 

 membranous coverings. The egg itself is semi-oval, its long axis 

 beincr 0-058 and its vertical axis 0'05 mm. There is a clear 

 space of 0-01 mm. between the outer covering and the inner 

 membiane. The medusiform embryo is 0-034 mm. long, and 

 its medio-vertical axis 0'024 mm. The embryonic hooks have a 



length of 0-017 mm. 



I have in a previous communication expressed ray conviction 

 from my own observations that Professor Huxley's views in con- 



