352 Mr. E. A. MiiicKin on the 



a proof to my mind that their acquaintance with Ascons 

 must have been practically limited to preserved specimens. 



It is my experience, on the contrary, that almost any species 

 of Ascon can be identified at sight when one is acquainted 

 with it, especially when it is living healthily or when pre- 

 served in a healthy and expanded condition — a state of things 

 not always found even in many specimens of Ascons sent out 

 by great zoological stations — and that the mode of growth of 

 the colony is a character of great generic value. It is true 

 that it is almost hopeless to recognize an Ascon by its exterior 

 from the figures given by Hackel, but that is hardly the 

 fault of the Ascons. Indeed, it is not too much to say that 

 the " Habitusbilder " given by Hackel, though no doubt of 

 great artistic merit, are practically useless for scientific 

 purposes. 



Apart from the interesting species /alcata, Hackel, I 

 recognize two main groups in the Ascons, which, perhaps, at 

 a later and more advanced stage of zoological science, will 

 attain to the rank of families or subfamilies, but which at 

 present must rank as genera *. In the first group are such 

 forms as coriacea, Mont., lacunosa, Johnston, reticulum, O. S., 

 clathrus, O. S., contorta, Bwk., blanca, M, M., iirimordialis^ 

 H., cerehriim, H., and spinoaa, Lend. In the second group 

 are hotryoides, Ell. & Sol,, complicataj Mont., LieberkuhnUy 

 O. S., and variabilis f H. 



In the first group, of which coriacea may be taken as the 

 type, the full-grown colony always has a reticulate form, and 

 the osculum has the value of a cloaca or vent. The form 

 typically assumed by members of this genus is that of a 

 dense reticulum of ramifying and anastomosing tubes, which 

 are usually of smaller diameter at the base and outskirts of the 

 colony, and gradually become enlarged as they approach the 

 osculum. Sometimes, as in the encrusting " leathery " forms 

 of coriacea, the tubes form a simple network in one plane, 

 from which the oscula rise perpendicularly. Sometimes the 

 point of attachment of the colony is drawn out into a single 

 long stalk, as in lacimosa, into one or several stalks, as in 

 blanca. The osculum may be very inconspicuous, or it may 

 be of relatively great diameter, forming a central basin with 

 raised edges, into which a system of tubes empties itself; or, 

 again, it may be narrow and elevated, shaped like a chimney, 



* It may become possible later to subdivide these groups on characters 

 of canal-system and so forth. Thus, in the group I have called below by 

 the generic name Clathrina, Gray, the two species cerebrum and reticulum 

 seem to diiier in some details from the other species of the genus. 



