ZOOLOGhY AND BOTANY, MICROSCOPY, ETC. 21 



astonisHng rapidity the JJlva around them. Though many nudi- 

 branchs lay freely, their eggs never come to maturity. 



Not a few of the lower animals and sea-weeds, without any care 

 whatever, thrive and multiply wonderfully. Some succeed but too 

 well, and timely removal is needed to check their excessive encroach- 

 ment. The physiognomy of the aquarium is indeed notably deter- 

 mined by the rapid growth of (what Humboldt would have called) 

 social organisms ; within its bounds, as in the " great and wide sea," 

 nature's operations overwhelm those of art. The struggle for life is 

 here instructively displayed under modified circumstances. The actors 

 are the same ; the theatre is new. 



Compound Tunicata take the lead among these " spontaneous " 

 productions. The graceful Botryllidae exuberate in both the northern 

 and southern tanks. A transparent species, Pseudodidemnum crystal- 

 linum, at present predominates above all others. During the previous 

 winter its abundant gelatinous masses stifled numbers of sponges and 

 anthozoans. Of simple ascidians, Ciona intestinalis reproduces most 

 copiously ; as one generation dies, its place is re-occupied by its suci' 

 cesser. Compared with ascidians, Bryozoa are not very generally 

 distributed. Bugula is now the commonest, especially in the compart- 

 ment for eels, where it flourishes along with Zoanthus and Hydradinia. 

 Mullet and some other fishes, hurtful to various low growths, soon 

 scour the rocks tenanted by ascidians. 



In luxuriance of growth the diatoms exceed all other plants. 

 They clothe not only the sides and floors of the tanks, but also their 

 less active inhabitants. Many zoophytes in this way become fatally 

 invested. The larger crustaceans, hypnotized by the unwonted cold 

 of last winter, were often covered with these Algae. Next in abun- 

 dance to diatoms come the Oscillariae. 



Few of the higher Algte thrive in the aquarium. Least delicate 

 seem the firmer species of Sargassum and Cystoseira, and two species 

 of Codium {bursa and elongatum). Most Floridese are evanescent in 

 captivity. Dr. Berthold has recently observed fruiting forms of 

 Chylocladia and Gallithamnion. 



The tank allotted to Annelids affords a spectacle of great beauty 

 and variety ; in short, it is a perfect microcosm. Of its inhabitants, 

 we can only note the young of a species of Spirorbis, a well-known 

 commensal of Palinurus. This annelid multiplies so fast that much 

 trouble is spent in removing its tubes, shaped like a post-horn, which 

 soon cement themselves with obstinate firmness to the glass windows 

 of the aquarium. 



Fishes, if we except Selachians, do not breed well in the aquarium. 

 Otherwise they are flourishing prisoners ; the conditions unfavourable 

 to their propagation have not yet been thoroughly ascertained. A 

 work by Costa, published in 1871, records the natural spawning 

 season of numerous fishes in the Gulf of Naples. 



Utilizing his own researches and those of others, Herr Schmidtlein 

 has drawn up a serviceable table, with notes on the reproduction and 

 development of several Neapolitan marine animals. The original 

 observer, in every case, is cited. 



