167 



SEXUAL REPRODUCTION IN THE MUCORIXI. 



By Du. Ant. de Bary. 



To the phenomena of fecundation already described is imme- 

 diately related the copulation of the Mucorini^ which has, as yet, 

 only been observed in two species of this family. The filaments 

 which conjugate in Rhizopus nigricans are solid, rampant tubes, 



ramified without order, and confusedly intermingle 1. Where two 

 of these filaments meet, each of them pushes towards the other an 

 appendage which is at first cylindrical, and of the same diameter as 

 these filaments themselves. From the first these two processes are 

 firmly applied to each other by their extremities; they increase in 

 size, become clavate, and constitute together a fusiform body placed 

 across the two conjugated filaments. Between the two halves of 

 this body there exists no constant difference of volume, and often 

 they are perfectly equal. In each there is an abundant protoplasm, 

 and when they have attained a certain development, the largest ex- 

 tremity of each is isolated by a septum from the clavule, which 

 thus becomes the support or suspender of the copulative cell. The 

 two conjugated cells of the fusiform body are generally unequal ; 

 the one is a cylinder as long as broad, the other is disciform, and 

 its length is only equal to half its breadth. The primitive mem- 

 brane of the clavule forms a solid partition between the copulative 

 cells, which is composed of the two lamella? ; but soon after these 

 cells become defined the medial partition is pierced in the middle, 

 and soon disappears entirely, so that the two twin cells are con- 

 founded in one single zygospore, that is to say, in one organ of mul- 

 tiplication, which is due to the union of two more or less similar utri- 

 cles. After its formation the zygospore still increases considerably 

 in size, and acquires a diameter of more than one-fifth of a mi lie- 

 metre. Its form is generally spherical, flattened on the faces, which 

 are attached to the suspenders ; or it imitates a slightly elongated 

 cask. The membrane thickens considerably, and consists, at the 

 time of maturity, of two superimposed teguments; the exterior or 

 epispore is solid, of a blackish-blue colour, smooth on the piano 

 laces in contact with the suspenders, but covered everywhere else 

 with thick warts, which are hollow internally; the endospore is 

 thick, composed of several layers, without colour, provided with 

 uarts corresponding to those of the epispore. The contents of the 

 zygospore consist of a large grained plasma, in which large drops 

 of an oleaginous liquid often float. While the zygospore is in- 

 creasing in size the suspender of the smaller copulative cell becomes 

 a rounded and stipitate utricle, often divided at the base by a par- 

 tition, and which attains almost the size of the zygospore. The 

 suspender of the larger copulative cell preserves its primitive form 

 and becomes scarcely any larger. It is rarely that there is not a 

 considerable difference in size between the two conjugated cells and 

 the suspenders. 



