. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. davenport: processes concerned in ontogeny. 183 stem strikes a curtilage or a vessel, its fibres are bent in different direc- tions and the stem divides. The resisting objects are thus considered by His to act in a mechanical, i. e. direct way. The results are, however, equally explicable by the response-to-stimulus theory. The splitting which occurs at the blind ends of developing blood-ves- sels and excretory tubules, and the repeated divisions of many glands — salivary gland (M. Fig. 334), liver, and lungs
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. davenport: processes concerned in ontogeny. 183 stem strikes a curtilage or a vessel, its fibres are bent in different direc- tions and the stem divides. The resisting objects are thus considered by His to act in a mechanical, i. e. direct way. The results are, however, equally explicable by the response-to-stimulus theory. The splitting which occurs at the blind ends of developing blood-ves- sels and excretory tubules, and the repeated divisions of many glands — salivary gland (M. Fig. 334), liver, and lungs (M., Fig. 445) —are exam- ples of this process. Other cases are found among Invertebrates, as, for example, the tentacles of many Cnidaria (K. & H., Figs. 27, 31), "roots " of Sacculina, and liver branches of Limulus (K. & H., Fig. 338).. b. The second case, that of division of a tubule throughout its entire length, is illustrated in the development of the segmental duct in some Vertebrates, and in the separation of aorta and pulmonary artery. (Figure 12). 3. Anastomosing, or the process of fusion of similar threads, thus forming a network, is of wide-spread occurrence. It is exemplified in the development of nerves (Figure 13) and blood-ves- sels in Vertebrates, and in some glands, especially the vertebrate liver. 4. Fusion with other Organs. The process of fusion of diverse organs will be studied in greater detail in other sections of this paper. It occurs, for instance, at the close of the process of growth of the neck of a mesenchymatous gland (or other independently arising tubule) towards its Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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