. Echinoidea . Kig. 3. Urechinus naresianus. Penstome and adjoining part frotn the inside. 2/,. succeeded in making clear the of the piates, either b\- treatino; it with alcohol-ghcerine, mount- ing it in Canada balsam or drying it. The most prominent featnre of the specimen is the position of the anal area, almost in the middle of the abactinal side. The snbanal fasciole is fainth- indicated; the spines are rather long, equalling in length the diameter of the test. The pedicellariæ are like those of the adnlt specimens, viz. the globiferons and small ophicephalous (see below), other
. Echinoidea . Kig. 3. Urechinus naresianus. Penstome and adjoining part frotn the inside. 2/,. succeeded in making clear the of the piates, either b\- treatino; it with alcohol-ghcerine, mount- ing it in Canada balsam or drying it. The most prominent featnre of the specimen is the position of the anal area, almost in the middle of the abactinal side. The snbanal fasciole is fainth- indicated; the spines are rather long, equalling in length the diameter of the test. The pedicellariæ are like those of the adnlt specimens, viz. the globiferons and small ophicephalous (see below), other kinds not being found. The peristomial tnbefeet are alread}- penicillate. The next size represented is 7-5""" in length. Here the anal area has reached near to the posterior end of the test, three pairs of piates being developed above it in the unpaired interambulacrum; the ventral side, however, projects still a little beyond the anal area, the posterior end of the test thns sloping a little downwards and ontwards, whereas in later stages it is vertically cnt, and in grown specimens the posterior end slopes downwards and inwards, the abactinal side projecting over the anal area, till at last the anal area is almost on the flat actinal side. The fi- gure 4 shows the of the anal area in the different stages. â The plastron and bivium in this specimen of 7-5""" has upon the whole the same form and relations as in the grown specimens. The subanal fasciole is distinctly developed. The apical system is essentialh- as in the grown specimens. â In the next stages I find no iniportant changes to notice. The}- become gradually higher, however, there is a rather great variation in the height in grown specimens, as remarked by Agassiz. The displacement of the periproct gi\-es the most promi- nent change. The genital openings appear rather late; I have not seen them in specimens smaller than 22""", but sometimes they do not develo
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1900, bookyear1903
