ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 463 



Life-History of Autolytus cornutus.* — Mr. P. Calvin Mensch dis- 

 cusses whether it is useful to speak of alternation of generations in the 

 life-history of this worm. The life-history includes : — (1) the develop- 

 ment from the egg of the parent stock ; (2) the development of sexual 

 products in segments posterior to the thirteenth setigerous segment, the 

 development of a head on the fourteenth, and the separation of these 

 segments for the formation of the free-swimming stolons, Polybostricus 

 <£ and Sacconereis 9 ; (3) regeneration of the lost segments and the 

 formation in this way of a second and possibly a third or fourth stolon ; 

 (4) finally the development in the parent stock of sexual products and 

 the conversion of it into a sexual individual. While the sexual 

 products are forming, the regeneration of lost segments is still taking 

 place ; but in none of the specimens found had this new growth gone 

 further than the formation of a small bud, consisting of no more than 

 eight or ten distinct segments. 



The above shows, not a sexual generation alternating with an asexual, 

 but at most no more than a sexual dimorphism — a sexual individual 

 budding off sexual stolons, and, as its own sexual products mature, par- 

 taking more or less of the epitokous form of other Syllids, and itself 

 becoming sexual. In short, instead of true alternation the author sees 

 simply a dimorphism resulting from an asexual multiplication of the 

 parent stock. 



Calciferous Glands in the Earthworm.f— The late Mr. N. E. 

 Harrington made a research on this subject. The calciferous glands have 

 two openings — (a) through the epithelial lining of the first pair of glands 

 into the oesophageal pouch ; (6) through the epithelium in the middle of 

 the fourteenth somite directly into the oesophagus. The latter opening 

 transmits only the milky fluid with its suspended crystals. These pro- 

 bably neutralise acid food, while the pebbles excreted from the anterior 

 pouches pass through the digestive tract unchanged. An excess of cal- 

 careous matter in the intestine does not increase the amount of lime 

 produced by the glands, although acid food does. Carbonate of lime is 

 formed, and appears as crystals inside the secretory cells. The nucleus 

 and the entire distal part of the cytoplasm disintegrate during active 

 secretion. The nuclei are replaced by smaller nuclei situated near the 

 blood-sinus wall, and around these the general cytoplasm of the syncy- 

 tium is built up into club-shaped cells. The smaller nuclei are derived 

 in turn from migratory elements which lie closely appressed to the 

 limiting membrane of the secretory lamellje, either in the blood or in the 

 glandular tissue. These migratory nuclei, or blood-corpuscles, are 

 derived in development from the amoeboid cells of the endoderm. The 

 plasma of the blood is also derived from these same cells of the endoderm. 

 The anterior pair of pouch-like glands are the only ones lined with true 

 epithelium, and are developed as diverticula of the oesophagus ; while the 

 two posterior pairs are formed by migration of the amoeboid endodermic 

 nuclei, which arrange themselves about cavities formed de novo near the 

 splanchnopleure, an i give rise to the secretory elements. In an appendix 

 the complex circulation is fully discussed. 



* Amer. Nat., xxxiv. (1900) pp. 165-72. 



t Journ. Morph., xv. (1899) Supplement, pp. 105-68 (4 pis. and 10 figs.). 



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