ON GYRODACTYLUS ELEGANS. 163 
is a spherical body, occupying nearly the whole of the cavity of 
the uterus. In the early stages of segmentation, several of the 
segment spheres are much larger than the rest, Fig. 49 ss, but the 
later stages are characterised by greater uniformity in the size of 
the spheres, Fig. 50. At an early stage in the development of the 
embryo the large hooks of the caudal disc are visible, Fig. 51 Th ote 
and, occasionally, one of the contractile vesicles may be seen con- 
tracting, wus. A little later, the marginal processes and hooklets 
of the caudal disc present themselves, Fig. 52, and at a still later 
period the uterus and oviduct are to be seen, Fig. 53 w¢s. Xovd. 
This point brings me to the consideration of a remarkable and 
interesting feature in the embryology of Gyrodactylus. The uterus 
of the developing embryo nearly always contains an ovum in an 
advanced stage of segmentation, Fig. 53 se. The hooks of the 
caudal disc may often be seen, while its oviduct contains a mature 
ovum, 0vm2. The oviduct of the parent also contains a mature 
ovum, ovmz. Supposing the development of the first embryo 
to be the result of ordinary impregnation, how are we to account 
for the development of the second, and in some instances observed 
by Wagener, of a third. My friend, Mr. C. H. Hurst, demonstra- 
tor in Biology at Owens College, to whom I mentioned having 
seen a single spermatozoon in the ovary, suggested that the ovary 
may prove to be a hermaphrodite gland, giving origin to both 
sexual elements. The entire absence of spermatozoa in the testis 
lends some colour to this suggestion, but I do not think the pre- 
sence of one spermatozoon in the ovary, which may have been 
purely accidental, warrants the adoption of Mr. Hurst’s view as a 
means of explaining the development of the second and third 
embryos ; and we niust not forget that Wagener records having 
repeatedly seen both spermatozoa and spermospores in the testis. 
On the other hand, if the development of the first embryo is proved 
to be the result of a sexual process, in which the genital armature 
described by Wagener is concerned, we are still in the dark with 
regard to the development of the second and third. Wagener 
suggests that “ portions of the first ovum from which the first gene- 
ration was produced, remain over, which even when contained in 
the embryo, repeat its formation.” If this is the case, what por- 
tions of the original ovum remain over ; and, as it is perfectly clear 
that this apparently asexual reproduction may go on indefinitely, 
at what period in the life history of Gyrodactylus elegans does sexual 
reproduction take place? These are questions to which I invite 
the attention of microscopists. 
DESCRIPTION OF FIGURES. 
Fig. 43. Gyrodactylus elegans—c 7, cephalic lobes; ™, mouth ; 
¢d., caudal disc ; 2 z, hooks of caudal disc ; 7/., lateral processes 
