. Fig. 9a. Amallocystis umbellatus , type specimen. Section preceding the one of Fig. 8/;. Organ of fixation with sieve plate. /, organ of fixation ;/•, root, x 163. Fig. 96. Amallocystis fagei Boschma, type specimen. Section of lower part of organ of fixation. /, organ of fixation; p, proto- plasmatic excrescences; s, sieve plate, x 283. that found in It must have had a strong cuticle, but the part of the organ of fixation to the left of the sieve plate in Fig. 9^ probably had a thin cuticle, so that the protoplasmatic excrescences (the roots) might absorb food from the host. Gr
. Fig. 9a. Amallocystis umbellatus , type specimen. Section preceding the one of Fig. 8/;. Organ of fixation with sieve plate. /, organ of fixation ;/•, root, x 163. Fig. 96. Amallocystis fagei Boschma, type specimen. Section of lower part of organ of fixation. /, organ of fixation; p, proto- plasmatic excrescences; s, sieve plate, x 283. that found in It must have had a strong cuticle, but the part of the organ of fixation to the left of the sieve plate in Fig. 9^ probably had a thin cuticle, so that the protoplasmatic excrescences (the roots) might absorb food from the host. Gradually the root system became more divided and more strongly developed; at the same time the number of external parts (trophomeres and gonomeres) increased, necessitating a stronger fixation of the parasite. The proximal parts of the root system now became covered with a thick and strong cuticle, thereby forming a part of the organ of fixation in securing a stronger hold of the parasite on its host. The sieve plate which was present between the organ of fixation and the roots now had lost its direct function, but it remained as it was, and the process of formation of a trabecular mass of cuticular excrescences even continued, so that now in some parts two rows of trabeculae are visible. In the type specimen of A. umbellatus the sieve plate therefore appears to be an organ which has had its use as long as the parasite was comparatively young and possessed a few trophomeres only. It has lost its real function now, but it has remained where it originally developed. A comparison with the sieve plate of A. fagei shows that the trabecular mass in A. umbellatus must be regarded as being homologous with the former. The internal part of the organ of fixation forms a more or less bulbous expansion which is protracted
Size: 3276px × 1525px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
