. Chordate morphology. Morphology (Animals); Chordata. Lamprey The egg of the lamprey {Figure 7-1 B) is ovoid in shape and covered by a chorion (shell and microvilli) and a vitelline membrane. There is a small opening, the micropyle, through the shell at the apex of the egg. The egg is essentially isolecithal, although there is an accumulation of larger yolk spheres at the vegetal end. With fertilization, the membranes lift from the egg surface, forming a perivi- telline space (Figure 7-6). The cleavages are as in Amphi- oxus, and the resulting blastomeres are fairly equal in size. A blastula
. Chordate morphology. Morphology (Animals); Chordata. Lamprey The egg of the lamprey {Figure 7-1 B) is ovoid in shape and covered by a chorion (shell and microvilli) and a vitelline membrane. There is a small opening, the micropyle, through the shell at the apex of the egg. The egg is essentially isolecithal, although there is an accumulation of larger yolk spheres at the vegetal end. With fertilization, the membranes lift from the egg surface, forming a perivi- telline space (Figure 7-6). The cleavages are as in Amphi- oxus, and the resulting blastomeres are fairly equal in size. A blastula is formed with a large blastocoel. The dorsal wall of the blastula is about two cells thick. Invagination begins with the formation of a blastopore groove at what will be the posterior end of the organism. Involution of cells occurs particularly at the dorsal blastopore lip; there is some epiboly, overgrowth by the dorsal lip. With the completion of invagination, a medullary plate forms along the dorsal midline. This plate gradually sinks as the outer neural ridges move inward to meet at the mid- line, thus forming a solid neural strand or keel. The blasto- pore remains open throughout the process of neural keel formation. As this keel is formed, the mesoderm and notochord I Z_sperm micropyle / '^. icrovilli â perivitelline space A FERTILIZATION. 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 Jollie, Malcolm. New York, Reinhold
Size: 1864px × 1340px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionameri, bookcollectionbiodiversity
