March 10, 1899.] 



SCIENCE. 



365 



anastomosing fibrous processes, which be- 

 come attached to the adjacent wall of the 

 body, or of the enteron, to form the larval 

 musculature. The others remain as paren- 

 chyma cells. 



Fission and Regeneration in Cerebratidus. C. 



B. Wilson. 



Foe three years, while investigating the 

 embryology of Cerebratidus lactam, Verrill, 

 very few perfect specimens were found at 

 the close of the breeding season, while there 

 were many with regenerating papillae. 

 Last summer a perfect male and female 

 were secured and kept for ten weeks. The 

 genital products were discharged simulta- 

 neously three different times at intervals of 

 several days. Then both worms dismem- 

 bered the posterior half of their bodies 

 without provocation. 



The anterior fragments at once regener- 

 ated, growing in three weeks' time papillae 

 measuring 50 mm. in the female and 38 

 mm. in the male. The posterior fragments 

 lived ten days and died without any signs 

 of regeneration. But others have been kept 

 alive several weeks under less favorable con- 

 ditions and have yielded perfectly healthy 

 sexual products. We are led to conclude, 

 therefore, that Cerebratidus often dismem- 

 bers voluntarily at the close of the breed- 

 ing season, but, while the anterior fragments 

 regularly regenerate, the posterior ones 

 seldom if ever do so. Careful anatomical 

 examination shows that actual fission is 

 accomplished chiefly by means of the trans- 

 verse muscles of the body-walls. There are 

 no indications of the rows of nuclei found 

 by Blenham in Carinella. 



Sections of papillae show that in regener- 

 ation the longitudinal muscles contain 

 numerous transverse fibers ; in the early 

 stages the two kinds are about equal. 



The large lateral nerve cords are regen- 

 erated from ectoderm cells. Two parallel 

 longitudinal invaginations appear on the 



ventral surface of the papilla. The ecto- 

 derm between them contains no gland cells; 

 a shallow longitudinal groove soon sepa- 

 rates this ectoderm into halves. In the 

 center of each half nerve fibers are formed 

 from modified ectoderm cells. 



They then migrate to their normal posi- 

 tion, while both groove and invaginations 

 quickly disappear and the ectoderm be- 

 comes filled with gland cells. 



Tlie Female Genital Tract in Melophagus. H. 



S. Peatt. 



Melophagus ovinus, a dipterous insect, is 

 peculiar because of the unusual length of 

 its uterine life, the young animal being born 

 as a fully grown larva. This long uterine 

 life has been the cause of a profound modi- 

 fication of the entire genital tract. The 

 uterus is unusually large ; two pairs of 

 glands pour a milk-like food into the uterus 

 which feeds the growing larva ; the prox- 

 imal portions of the oviducts are fused and 

 function as a permanent receptaculum sem- 

 inis ; the ovary possesses a very thick 

 peritoneal covering composed of branched 

 muscle and connective- tissue fibres which 

 forms a sac and encloses the two ovarioles ; 

 these are composed each of two follicles and 

 a germarium, no terminal thread being 

 present, and are attached by the germarium 

 to the inner distal surface of the peritoneal 

 sac, their lower ends hanging free within 

 the sac. There are thus in the two ovaries 

 at any one time eight follicles, each contain- 

 ing a developing ovum. A single egg is pro- 

 duced every two to four weeks ; it passes into 

 the uterus, being fertilized on the way, and 

 there remains two to four weeks until the 

 young animal is born, an old larva. The two 

 ovaries, and within each ovary the two ovari- 

 oles, alternate in furnishing the next egg. 



Intracellular Differentiations in Gland Cells 

 of Phascolosoma Gouldii. Maegaeet Lewis 



NiCKEESON. 



In the epidermis of this Gephyrean are 



