. Elements of Comparative Anatomy. GENEEATIVE OEGAXS OF ECHIXODEEMA. 225 system is simple in structure, the excretory ducts are not com plicated, and there is no intromittent organ, so that the surrounding* water is the medium of communication in impregnation. On the whole there is a great resemblance to the corre- sponding structures found in Vermes. The lowest stages, both as to num- ber, arrangement, and as to the more special characters of the organs, are seen in the Asteroi'cla. The testes or ovaries are tubular or lobate glan- dular canals, which in some forms are arranged in two rows, a
. Elements of Comparative Anatomy. GENEEATIVE OEGAXS OF ECHIXODEEMA. 225 system is simple in structure, the excretory ducts are not com plicated, and there is no intromittent organ, so that the surrounding* water is the medium of communication in impregnation. On the whole there is a great resemblance to the corre- sponding structures found in Vermes. The lowest stages, both as to num- ber, arrangement, and as to the more special characters of the organs, are seen in the Asteroi'cla. The testes or ovaries are tubular or lobate glan- dular canals, which in some forms are arranged in two rows, and disposed conformably with the metamerism of the arms (Ophidiaster, Ai'chaster). In others there are only two groups in each arm, which may extend along the whole cavity of the arm (this is the case even in Brisinga), or may be limited to the interradial space merely (Fig. 108, ;/). A comparison of these characters shows us, that there is a gradual reduction in the number of the generative glands, which corre- sponds with the gradual centralisation of the organism, which we have. Fig. 114. Generative organs of an Ophiurid (Opliioderma lougicauda). The dorsal integument and the digestive organs have been removed. ';• Arms, g Ovarian 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 Gegenbaur, C. (Carl). London : Macmillan
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